So it was a big deal when Apple (AAPL) announced a new service that, for $100 a year, would bring corporate-type synchronization of email, calendars and contacts to anyone. It was even better that Apple promised that the service, called MobileMe, would work on Windows computers as well as on the company’s own Macintosh computers, iPhones and iPod Touch hand-helds. To top it off, Apple threw in 20 gigabytes of online storage, a suite of Web-based applications, the ability to synchronize browser bookmarks and an online photo gallery.

Unfortunately, after a week of intense testing of the service, I can’t recommend it, at least not in its current state. It’s a great idea, but, as of now, MobileMe has too many flaws to keep its promises.

I am not referring to the launch glitches that plagued MobileMe earlier this month, such as servers that couldn’t keep up with the traffic and email outages that, for some users, persist as I write this. Those were bad, but they have eased considerably. Apple already has apologized for them and is giving customers an extra 30 days on their subscriptions to make up for the poor start. The problems I am citing are systemic.

Here’s how it’s supposed to work. You subscribe to MobileMe and set up a new MobileMe email account, which can also suck in email from your current address. Your MobileMe email is pushed to your Windows computer using your choice of Microsoft (MSFT) Outlook, Outlook Express or the new Windows Mail program. It’s also pushed to your Mac using the built-in Apple Mail program. And it shows up instantly on your iPhone in the phone’s built-in email program.

Similarly, if you add, delete or change a calendar entry or a contact on any of the devices, the change automatically is reflected on all the others. In Windows, the MobileMe calendar shows up in Outlook, and the contacts can be viewed in Outlook, the Windows Address Book or Windows Contacts. On the Mac, the calendar and contacts appear in the built-in iCal and Address Book programs. On the iPhone, MobileMe uses the built-in Contacts and Calendar programs.

Bookmarks can be synchronized using either the Mac or Windows versions of Apple’s Safari Web browser, or Internet Explorer 7 on Windows.

At the MobileMe Web site, using any computer, you can send and receive email via a Web-mail program, and view and edit your calendar and contacts. Changes made on the Web site instantly show up on your computers and your iPhone, and vice versa. Also at the MobileMe Web site, you can maintain a photo gallery and view your online file storage.

But in my tests, using two Macs, two Dell (DELL) computers and two iPhones, I ran into problem after problem. One big issue is that while changes made on the Web site or the iPhone are instantly pushed to the computers, changes made on computers are only synced every 15 minutes, at best. Apple has admitted that this is a problem, and says it is working on it.

But there’s more. The Web site was sluggish, and occasionally calendar entries wouldn’t load at all. Sometimes, you have to manually refresh the Web pages to see changes made on your devices. And when I tried to open my Web-based file-storage page directly from the MobileMe control panel on Windows, I got an error message on both Dells.

My MobileMe calendar, which originated on a Mac, didn’t flow into the main Outlook calendar, but appeared as a separate calendar in Outlook, which was visible only by changing settings. My address-book groups on the Mac, which are simply distribution lists, didn’t show up as distribution lists in Outlook, but as separate address books, and they also weren’t immediately visible. Apple blames Outlook quirks for these issues, but in my view, it should have overcome them.

Other problems abounded. On one occasion, my synced contacts on the iPhone appeared as names only, without any information. In general, synced contacts on the iPhone loaded slowly.

When my Apple Mail program used rules I had set up to automatically file certain emails into local folders instead of leaving them in the inbox, they simply disappeared from my MobileMe account on the iPhone and the Web site. Avoiding this requires a tedious editing of all your rules.

Twice, MobileMe was unable to sync my bookmarks at all, and when it did, their order was scrambled. When I synced contacts to my iPhone, my custom ringtones for particular contacts were lost and had to be reselected.

Apple patiently explained each of my problems, sometimes helping me with workarounds, sometimes claiming they were rare, other times saying that it was working on fixes.

If Apple does get MobileMe working smoothly, it could be a terrific service. But it’s way too ragged now.

• Find all of Walt Mossberg’s columns and videos online, free, at the new All Things Digital Web site, http://walt.allthingsd.com. Email him at mossberg@wsj.com.

Beginning this summer, as soon as next month, wireless Internet access will arrive in the passenger cabins of some commercial U.S. airliners.

On these Internet-equipped planes, any passenger with a Wi-Fi enabled laptop — or a cellphone with Wi-Fi — will be able to do almost everything he or she could do online at home or at the office. That includes surfing the Web, using email, having instant-messenger text chats, downloading and uploading files, and streaming video and audio.

In fact, I did all these things a few days ago on a test flight using the new system, called Gogo. During the flight from San Francisco to Denver, on a small test jet, I could operate online as if I were sitting at my desk, or in a Starbucks. I used Dell (DELL) and Apple (AAPL) laptops, a BlackBerry (RIMM), a Windows Mobile phone and an iPhone to perform all the most common online tasks, while soaring over majestic mountains and glorious national parks.

I sent and received emails on Microsoft (MSFT) Outlook and Apple Mail, including messages with hefty attachments. I conducted IM chats on AOL (TWX) Instant Messenger and Google (GOOG) Talk. Using all the major Web browsers, I called up dozens of Web sites, and watched video clips on Hulu and YouTube. I downloaded photos, songs, PDF files and Microsoft Office documents. I used all the Internet functions on the iPhone, and on the Wi-Fi-equipped BlackBerry and Windows Mobile phone.

One important caveat: Gogo is a data-only system. It doesn’t allow phone calls and will block all services that allow voice conversations to be made over the Internet.

Gogo will launch on three American Airlines (AMR) routes, likely in July. The first planes to use it will be American’s 15 Boeing 767s flying between New York and Los Angeles, San Francisco and Miami. Later in the year, Gogo will be available on all of Virgin America’s small number of routes, and possibly additional American routes, if the first deployment works well. It’s supplied to the airlines by a Denver-based company called Aircell, which says it is in negotiations to offer the Gogo service on several other major U.S. airlines by next year.

The Gogo service will cost a flat fee of $12.95 for flights of three hours or longer, and $9.95 for shorter trips. You log into Gogo as you would any commercial Internet service, registering on a special Web page. Aircell plans to allow advance sign-up, so you’d only have to enter an ID and password on the plane. No add-on software, hardware or cables are required.

A few Web functions will be offered free from Gogo, including access to the American Airlines Web site, to Frommer’s online travel guides and to a limited selection of articles from The Wall Street Journal.

Gogo isn’t the first in-plane Internet service. A few years ago, Lufthansa (LHA.MU) offered a satellite-based service from Boeing (BA), mainly on over-ocean flights, but it was canceled.

The service operates at respectable, if not blazing, speeds — similar to what you’d get on a cellular broadband service or a slow home DSL line. On my test flight, download speeds varied from 266 kilobits per second to about 1.4 megabits per second, with the most typical speeds hovering between 500 and 600 kbps. Upload speeds were between 250 and 300 kbps. I found that most of the tasks I tested, except for streaming video, felt smooth and normal.

Speeds could degrade on a large plane with scores of people online simultaneously. But Aircell claims it has the technology to make my experience representative for anyone doing common tasks, such as Web surfing and email. During my test flight, eight laptops and six Wi-Fi-enabled smart phones were using the system simultaneously. All registered decent speeds, except for a couple of minutes when the plane was crossing between the zones controlled by the company’s ground-based towers.

Aircell gets Internet access to the planes through a network of 92 towers scattered across North America. These essentially are cellphone towers, carrying a high-speed cellphone data signal, except that the Aircell antennas point up, into the sky. A receiver on the underside of the aircraft picks up the signal, which is then distributed through the plane via Wi-Fi.

The companies say Gogo is safe and won’t interfere with the plane’s operation. It is government-approved, and pilots can shut the system off should they deem it necessary.

Gogo has some limitations. The service plans to allocate its capacity so that low-bandwidth activities like Web surfing and email take priority over high-bandwidth ones like streaming video. That means you may find video to be slow and halting.

And Gogo is a North American, land-based service only. It won’t work over the oceans and, for now, it won’t work on other continents.

But for U.S. travelers who want to stay connected in the air, Gogo does the job.

• Find all of Walt Mossberg’s columns and videos online, free, at the new All Things Digital Web site, http://walt.allthingsd.com. Email him at mossberg@wsj.com.

The arrival of a large update like this isn’t a sign of trouble, or even unusual. Microsoft has routinely issued these large “service packs” periodically for Windows. And just this week, its competitor, Apple, unleashed an even larger update for its new operating system, Leopard.

Even though they can take a long time to download and install, such updates are generally a good thing for consumers. Microsoft will automatically deliver SP1, as the company calls it, through its normal updating mechanism, built into Windows. The update is free.

However, based on my tests of Vista SP1, I believe that for most average consumers, it will likely be a nonevent, and for others it will be disappointing. Many of its benefits are aimed at corporations and power users, or are under-the-hood fixes that are hard to discern. For mainstream users, it adds no significant, visible features to Vista, and changes little or nothing about the way the operating system looks and works.

Also, SP1 doesn’t resolve some of the most annoying flaws in Vista, including slow start-ups and reboots, and a security system that nags you too much and requires add-on anti-virus software. I guess these problems will either never be fixed fully or will have to wait for SP2.

While Vista SP1 does deliver some performance improvements in certain scenarios, it can actually temporarily degrade performance — including making reboots even slower — because of a quirk in the update process. This slowdown should go away in a few days, the company says.

On balance, the update is probably worth installing, especially since Microsoft will deliver it automatically. But I wouldn’t rush to grab it and I wouldn’t expect much from it. One note: you can’t install SP1 until you have installed a couple of other patches first. These will also be distributed automatically.

I installed Vista SP1 on two computers that had come with the original Vista preinstalled: a 10-month-old Sony Vaio SZ laptop and a two-month-old Dell XPS One desktop. Because the automatic download distribution isn’t yet in place, Microsoft sent me the update on a disk, which also included the prerequisite patches. In each case, the upgrade took a little over an hour and went smoothly. During the process, the computers rebooted multiple times, but it was all automatic and didn’t require user intervention.

After the installation, the computers functioned normally. I tested three of the performance improvements Microsoft claims for SP1. The first involved speeding up the copying of hefty folders containing large numbers of files. On both machines, copying a folder containing over 700 files totaling almost 700 megabytes took less than half as long with SP1 as it had with the original Vista.

I also tested how long it took both machines to awaken from a hibernation or sleep state and be ready for work. For these tests, I began with each machine running Microsoft Word, Microsoft Outlook and the Firefox Web browser, then I forced them into sleep and hibernation mode.

By my definition, “ready for work” means that Vista’s circular delay indicator has gone away, the software that loads at start-up has finished launching and the computer has fully reconnected to its wired or wireless network. On both of my test machines, SP1 improved the recovery time from sleep or hibernation, shaving one to 10 seconds from the procedures.

Microsoft doesn’t claim SP1 will improve the speed of cold starts and reboots under Vista, but I tested these anyway. To my horror, I found that SP1 actually made rebooting — already slower than on comparable Windows XP computers or Macintoshes — even slower.

Microsoft explained that this was due to the fact that installing SP1 erases certain data used by Vista to speed up program launching. It takes the system a few days to build this data back up, the company says. Until then, it says, overall performance, including reboots, can be slower under SP1 than under original Vista.

Microsoft provided me with a method that would rebuild this program-launching data more quickly, at least for the common programs I was using in my tests. Once I followed that method, rebooting time returned to its former state — still too slow for my taste, but at least not worse.

In briefing me on SP1, Microsoft made a big point of saying that great progress had been made in the past year in making Vista work properly with add-on devices, such as printers. I tried my 2003-vintage Hewlett-Packard printer, which hadn’t worked properly with the original Vista. It still didn’t work well with SP1.

So, Vista SP1 is a step forward, at least after a few days of use. But it’s not a big step.

Email me at mossberg@wsj.com. Find all my columns and videos online, free, at the new All Things Digital Web site, http://walt.allthingsd.com.

On Jan. 15, Microsoft will be releasing its first new version of Office for the Mac in nearly four years. It is called Office 2008, and it has two big changes from the current version, Office 2004.

For one, it is the first edition of Mac Office designed specifically for the new Intel-based Macs that Apple began rolling out two years ago. While the old Office ran adequately on the new Macs, it was slow to launch and slow to perform certain operations.

Second, the new Mac Office now reads and writes a new set of file formats Microsoft introduced a year ago in the latest Windows version of Office, called Office 2007. Mac owners receiving files in these new formats had been forced to employ separate and clumsy file converter programs.

Now, once again, the Mac version of Office can handle all the same Word, Excel and PowerPoint files — in both old and new formats — created in Windows and vice versa. No translation or conversion is necessary. The files just open and save as they do in the Windows version.

I’ve been testing the new Mac Office on two different Intel-based Macs: an early MacBook Pro laptop and a new iMac desktop. On both machines, Office 2008 launched and ran far more rapidly and smoothly than Office 2004 did.

I also tested Office 2008 with a variety of documents created in the Windows version using the new file formats, which can be identified by four-letter file name extensions that end in the letter “x.” All opened rapidly and perfectly in the new Mac version.

As in the latest Windows version, the new Mac Office 2008 allows you to opt to continue to save automatically all your files in the old, familiar formats-DOC for Word, XLS for Excel and PPT for PowerPoint. But, if you want to switch to the new formats, or need to use a file you receive that was created in them, you can now do so with ease.

Like its predecessors, the new Mac Office differs in one major respect from its Windows cousin: It lacks Outlook, the famed, if bloated, program for handling email, calendar and contacts. Instead, Office 2008 has a new version of Microsoft’s Mac counterpart to Outlook, called Entourage, which performs the same tasks but doesn’t use Outlook’s file format. Like Outlook, Entourage can work with the Microsoft Exchange servers used by corporations, as well as with consumer email systems.

Office 2008 for the Mac has some new features, but it isn’t nearly as radical an overhaul as the latest Windows version was. While the latter junked all the menus and traditional toolbars in Word, Excel and PowerPoint, the new Mac version retains the familiar menus and toolbars. It doesn’t use the so-called Ribbon, a band of icons that is the signature feature of Windows Office 2007.

The new Mac Office, however, does include a new user-interface feature called the Elements Gallery, a narrow strip across the top of the document that lets you easily summon and insert canned features for laying out documents. For example, in Word, you can quickly insert a handsome cover page. In Excel, you can rapidly add a specific type of chart or a spreadsheet preconfigured, for instance, as an invoice. In PowerPoint, you can quickly add customized slide themes and layouts.

There is also a Publishing Layout View in Word that speeds the creation of things like newsletters, and a Ledger Sheet feature in Excel for creating home and small-business budgets.

In my tests, I ran into a few minor glitches. I had to edit my rules for sorting email in Entourage to get them to work and, at first, I was unable to add new spellings to my custom dictionary in Word, though that problem went away. But, generally, the program worked well.

The standard edition of the new Office costs $400, or $240 to upgrade your current version. There is a deluxe edition, which includes a professional media-management program, for $500, or an upgrade price of $300.

For most average users, however, I recommend the Home and Student edition for just $150 that can be legally installed on up to three different Macs. This inexpensive edition has full versions of Word, Excel, PowerPoint and Entourage, but doesn’t work with Exchange servers.

Microsoft is also running a sale, through Jan. 14, under which anyone buying Office 2004 gets a coupon that allows them to receive the high-end version of Office 2008 for just a shipping and handling fee of $6.99.

Microsoft Office 2008 for the Mac is a solid program that I can recommend for anyone with a new Mac. It’s not revolutionary, but it does the job.

Email me at mossberg@wsj.com. Find all my columns and videos online, free, at the new All Things Digital Web site, http://walt.allthingsd.com.

But in recent weeks, I’ve been bombarded by reader emails asking for Mac-buying advice. So, here’s a quick guide — a sort of Mac FAQ — to shopping for a Macintosh. As with my Windows guides, this is aimed at average, mainstream users doing typical tasks, not techies or businesses or hobbyists.

Q. Who should consider a Mac?

A. Pretty much every average consumer using a computer should at least look at the Mac. It combines gorgeous hardware with an operating system I consider superior to Windows, with better built-in software. It can even run Windows programs if you buy and install a copy of Windows. And unless you do that, you won’t be vulnerable to the vast array of viruses and spyware that threaten Windows users. Only a handful, so far, have been written to run on the Mac operating system, OS X.

Q. Who shouldn’t consider the Mac?

A. People who spend much of their time playing cutting-edge games should stick to Windows computers, because there are far fewer games written for OS X. Apple doesn’t offer hardware tuned for serious gaming. People looking for the lowest-price PCs should also avoid the Mac, because Apple’s cheapest model, the Mac Mini, costs $599.

Another group that should shun Apple’s computers are people who depend for support on corporate IT departments that are either ignorant about, or hostile to, the Mac. Finally, if you know and like Windows, and expect mainly to use Windows programs, stick with a Windows PC.

Q. Can I run Microsoft Office on a Mac?

A. Yes. Microsoft makes a Mac version of Office, which uses the same file formats that Word, Excel and PowerPoint for Windows have used for years. A new version of Office for the Mac is due in January and it will handle the new file formats Microsoft introduced this year. But the Mac version of Office omits Outlook. It has a similar program called Entourage, but Entourage can’t use Outlook data files. If you want a Mac but must have Outlook, you will have to install Windows.

Q. Can I use all my Windows files on a Mac?

A. Out of the box, Macs can handle all the common file types Windows machines create, including text files, pictures, songs and Adobe PDF files. The Mac even comes with a simple word processor that can open Microsoft Word files.

However, some specialized Windows programs create files that the Mac can’t handle out of the box. And the Mac version of Quicken has a difficult time properly handling Windows Quicken files. If you are a Quicken fan, install Windows and run the Windows version.

Q. Can I mix Macs and Windows on the same home network?

A. Macs can plug and play with most brand-name wired and wireless routers, and can share Internet connections with Windows PCs.

Q. How are Macs at Web surfing?

A. Fine. Apple’s built-in Safari browser is very good and the Mac version of Firefox is essentially identical to the Windows version. However, Macs lack an up-to-date version of Microsoft’s Internet Explorer, so you will have to install Windows if you need IE.

Q. Can Macs run standard peripheral hardware?

A. Macs can run nearly all keyboards, mice and printers that use USB connections, even ones that don’t explicitly say they run on Macs.

Q. What desktops does Apple offer for consumers?

A. Apple’s main consumer desktop is the one-piece iMac, which I regard as the best consumer desktop on the market. It comes in four models, with built-in 20-inch or 24-inch, flat-panel screens at starting prices ranging from $1,199 to $2,299.

Q. How about Mac laptops?

A. There are two. The entry-level MacBook has a 13-inch screen and a starting price of $1,099. The high-end MacBook Pro comes with either a 15-inch or 17-inch screen and starts at $1,999. Apple currently doesn’t offer a smaller laptop for road warriors, but there are persistent rumors that it will do so soon.

Q. What minimum specs should I look for on a Mac?

A. All Macs come with at least one gigabyte of memory — twice the minimum required for the new version of OS X, called Leopard. If you can, get two gigabytes. Apple charges a lot for extra memory, but you can buy it for less at stores and online providers.

Macs use the same dual-core Intel processors and graphics systems as many mainstream Windows computers; and, as with Windows, I wouldn’t pay extra for greater processor speed.

The iMac comes with at least a 250-gigabyte hard disk, and Mac laptop hard disks start at 80 gigabytes. Mainstream Windows desktops typically start with larger hard disks. But Apple offers much larger disks as options, which you should consider if you store a lot of photos, music and video files.

Email me at mossberg@wsj.com. Find all my columns and videos online free at the new All Things Digital Web site, http://walt.allthingsd.com.

The result is a polished, fairly powerful email program that I prefer to Google’s much-hyped Gmail, which is undergoing an even longer gestation. It has been in beta status since April 2004.

I’ve been testing the new Yahoo Mail on both Windows and Macintosh computers. It has some downsides, but it beats Gmail, in my view, both in terms of features and in terms of its ability to act like a standard computer program rather than a Web page, something for which Gmail often gets more credit.

A closer competitor to Yahoo Mail is actually Microsoft’s Hotmail, now called Windows Live Hotmail. But Yahoo tops Hotmail, too, in my opinion.

The new Yahoo Mail, which works in Internet Explorer and Firefox on Windows, and in Firefox on the Macintosh, is now more than just an email program. Like Gmail, but unlike Hotmail, it has a built-in instant-messaging module. You can choose to communicate with any of your contacts via a real-time chat, right from within Yahoo Mail, as long as that contact is online and has an IM account on either the Yahoo or Microsoft instant-messaging networks. You don’t need to be running your IM program.

Unlike either of its competitors, however, the new Yahoo Mail also allows you to exchange text messages with people on cellphones, although the message exchange must be initiated from Yahoo Mail.

Yahoo Mail offers unlimited storage of emails and attachments free of charge, and a very fast and good search capability — like Gmail’s — so you can keep years of messages on hand and retrieve them quickly. Gmail offers 2.9 gigabytes of storage free. It sells extra storage for prices ranging from $20 a year for six gigabytes to $500 a year for 250 gigabytes. Hotmail is in the process of boosting its storage to five gigabytes, free, and 10 gigabytes for $20 a year.

With Yahoo Mail, you can send attachments of up to 10 megabytes per message and 20 megabytes if you opt for a $20-a-year plan that also eliminates the annoying banner ads that litter the free version. Gmail offers attachments of up to 20 megabytes free. Hotmail allows 10 megabyte attachments and 20 megabytes under its $20-a-year plan, which also banishes ads. Gmail has no banner ads, just text ads that run alongside the emails and can’t be eliminated.

This new Yahoo Mail is gradually being rolled out in coming weeks. The company still plans to retain the older version of Yahoo Mail, now called Classic, for people who prefer it, or for those using browsers that are incompatible with the new version, such as Apple’s Safari.

The new Yahoo Mail allows you to do things that once were impossible in a Web-based email program. For instance, you can drag messages to new folders, or select a group of messages in the same way you would with a standard email program, to delete them or mark them as read or unread. Unlike in Gmail, when you right-click on a message you get a list of options that pertain to the mail program — like “Reply to Sender” — instead of options that pertain to the use of the browser — like “Add to Favorites.”

Also, Yahoo Mail features a very nice tabbed interface that Gmail and Hotmail lack. With this interface, which is separate from the browser’s own tabs, you could have your inbox in one tab, an instant-message or text-message conversation going on in another and a new email you are composing occupying yet another. You can move among these tabs without losing the content in any of them.

And like Hotmail but not Gmail, Yahoo Mail offers a preview pane, like Microsoft’s Outlook, so you can see the contents of an email without opening it. Gmail offers just a “snippet” of the message content. Unlike Gmail, which forces you to view your emails as bunched-up “conversations,” Yahoo Mail — like Hotmail — displays them as a standard email program does, sorting them by date, sender, subject or size.

So what are the downsides of Yahoo Mail?

Well, the biggest is probably that unless you pay for the $20-a-year premium plan, you can’t view your Yahoo mail account in a standard email program such as Outlook or Apple Mail. Gmail allows this free of charge. Hotmail allows it free in Outlook and in Windows Mail, though it will soon announce the capability for other email programs for premium members and, eventually, for free members as well.

Also, I found Yahoo Mail could sometimes be slow. When I created a new folder and tried to drag 200 emails into it, I was warned that I couldn’t do that because the new folder was “still being created.”

But overall, Yahoo did a really good job making its online mail program versatile, powerful and accessible.

Email me at mossberg@wsj.com. Find all my columns and videos online free at the new All Things Digital Web site, http://walt.allthingsd.com.

In classrooms and offices, homes and coffee shops, Macs are far more visible in the U.S. than they were just a few years ago. Part of this success results from the fact that Macs are excellent machines that handle the most important and common tasks as well as — or better than — computers running Microsoft Windows.

But the new popularity of the Mac is also partly due to the fact that it can now run Windows along with Apple’s superior Mac OS X operating system. That means that if there’s a program you need that comes only in a Windows version, you can run it on any current Mac model, speedily and with all its features.

Starting next week, there will be a new way to do this. A company called VMWare, long the leader in what’s called “virtualization” — running multiple operating systems simultaneously on a single computer — will be selling a program called Fusion that allows Windows, and Windows programs, to run on a Mac.

I’ve been testing Fusion, and I’ve found it works well. For instance, as I write this column on a Mac laptop using the Mac version of Microsoft Word, Fusion is allowing me to simultaneously run several popular Windows programs — Microsoft Outlook, Windows Media Player and Internet Explorer. Each is running in its own window, just as if it were a native Mac program. I can switch from one to the other rapidly and smoothly. Their icons show up on the Mac’s “Dock,” just like the icons for Mac programs.

In my tests, Fusion never slowed down my MacBook Pro laptop or two other Macs on which I tested it. As I write this, the Mac version of Word and all three Windows programs are performing normally, even though I am also running five other Mac programs. My MacBook Pro, which isn’t the latest or most powerful model, has two gigabytes of memory and an Intel processor that is a generation behind the current model.

Fusion, which will be available for $80 at vmware.com, becomes the third major option for running Windows software on a Mac. It will go up against a fine program called Parallels Desktop, also available for $80 at parallels.com and at retail stores. The third option is Apple’s own Boot Camp, currently a free product available at apple.com/bootcamp. Boot Camp will become a built-in feature of the next version of Apple’s Mac OS X operating system, due in October.

All three programs require users to purchase a full version of Windows and install it on the Mac. Like Fusion, Parallels is a virtualization program that allows you to run Windows and Windows programs simultaneously with the Mac operating system and Mac programs. Boot Camp works differently: It requires that you restart the Mac to switch into Windows, and it runs only one of the operating systems at a time.

In my tests, I compared Fusion and Parallels, which is its closest competitor. I used Windows XP Professional. Each also works with the new Windows Vista (and with older versions of Windows and various versions of the Linux operating system). But Microsoft has imposed a legal prohibition on installing the most common consumer versions of Vista, Home Basic and Home Premium, via virtualization programs.

The two programs are very similar. In most scenarios, they function nearly identically. Both allow you to run the full Windows desktop either in a window on your Mac or in full-screen mode. Alternatively, both allow Windows programs to float on their own, with the Windows desktop hidden, so they look and feel just like Mac programs. Both permit you to fetch and save files from folders already on your Mac. Both support copying and pasting between Mac and Windows programs. Both automatically use your Mac’s Internet connection.

Parallels has more features than Fusion. It comes with a set of utilities Fusion lacks, such as a program that can migrate the contents of a physical Windows PC into a Parallels virtual Windows PC, and another that allows you to retrieve files from the virtual Windows machine even when Parallels isn’t running. Parallels also has a nice feature that lets you assign any file to automatically open in a Windows program instead of a Mac program. And it makes it much easier to use a printer over a network than Fusion does.

But I found Fusion puts less strain on the computer overall. While I like Parallels and have used it since it came out, it sometimes slows down my Mac, especially when it is starting up Windows or performing some other major task. Fusion has a much smaller impact on the Mac’s overall performance.

You won’t go wrong with either program. Both give the Macintosh a level of versatility that can’t be matched by Windows-only machines.

• Email me at mossberg@wsj.com. Find all my columns and videos online free at the new All Things Digital Web site, http://walt.allthingsd.com.

The FlipStart is part of a new wave of tiny Windows PCs, which include the second version of a machine called the OQO, the Ultra-Mobile PC from Samsung and Sony’s UX series. For a decade or more, the computer industry has been trying to come up with an ultracompact computer that can use standard operating systems and software. They have failed to catch on broadly for several reasons.

First, they are an awkward, in-between size: too large to fit in a pocket, but too small to allow for minimally comfortable touch-typing keyboards. Second, their screens are often too small to handle the navigation through multiple windows that Windows requires. Third, their battery life has been poor. Finally, they’ve been very costly.

I’ve been testing the FlipStart and found that while it overcomes some of these issues, it can’t lick all of them. It runs Windows OK and it even has decent battery life. Its screen resolution and navigation are also pretty good. It weighs just 1.75 pounds, and is smaller in length and width than a standard paperback novel.

But its price, $2,000, is very expensive for a computer that’s too small to be very good for typing, yet isn’t small enough to be extra portable. Part of the size problem is that it’s thick — thicker than a 400-page paperback. And I found its keyboard to be too little and crude for laptop-style typing, but too wide for fast thumb typing, like people do on a BlackBerry. It also exhibited some funky behavior in my tests.

So, like its predecessors and competitors, the FlipStart is likely to be a novelty or niche product. It may be popular with some techies, but it’s no match for a small standard laptop, like Lenovo’s X models, which start at $1,250, are 2.7 pounds, are thinner than the FlipStart, and include a great keyboard and a screen that’s more than twice the size of FlipStart’s.

The FlipStart, which goes on sale March 27 on the company’s Web site, flipstart.com, is also much larger and heavier than the new second model of the OQO, which weighs just one pound. The new OQO, on sale next week at oqo.com, is also less costly, starting at around $1,500. Like the OQO, the FlipStart can also run the new Windows Vista, as well as Windows XP.

The FlipStart is designed as a clamshell, with a flip-up lid, like a laptop. It can be used in an L-shape, like a laptop, on a desk or table. The OQO’s keyboard slides down from behind its screen and you type on it while holding it vertically, like a smart phone. The FlipStart can be used that way, too.

The FlipStart’s 5.6-inch screen is bright and vivid, and it has a resolution of 1,024 by 600, less than most laptops, but much better than the new OQO’s. There’s a zoom feature that can be adjusted with a handy scroll wheel on the side, which is also used for scrolling through text.

There’s also a second, tiny screen in the lid, so you can see your email, contacts and calendar when the FlipStart is closed. Special navigation software on the main screen offers the same information.

In my tests, the FlipStart handled Microsoft Word, the Firefox Web browser, Picasa photo software and Apple’s iTunes quite well.

In my tough battery test, in which I turn off all power-saving software, turn on the Wi-Fi, crank up the screen brightness and play music endlessly, the FlipStart did surprisingly well. It clocked in at about 2.5 hours, which means you’d get three hours or more with typical usage. The slimmer, lighter new OQO got just 1 hour, 48 minutes.

The FlipStart includes both Wi-Fi wireless networking and a built-in cellphone modem that uses the fast EV-DO network. Both worked in my tests, as did wired networking via a snap-on port replicator that lets you connect a full-size monitor, keyboard, mouse and speakers.

But I ran into some problems. The unit too often failed to connect to Wi-Fi networks. Also, at one point, the FlipStart logged me out of Windows every time I typed the letter “L” in any program. Microsoft Outlook crashed on me repeatedly.

The keyboard, despite its typing flaws, has some nice aspects. It includes a touch pad and a pointing stick, to replace a mouse, and special keys for quickly performing various functions, such as getting to the desktop and switching open windows. But for thumb typing, I much preferred the OQO keyboard, even though it’s smaller and even though FlipStart commissioned a study showing its keyboard was better.

I think the solution to making better hand-held computers is in ever-more-potent smart phones, like Apple’s forthcoming iPhone, rather than in shrunken laptops like the FlipStart.

• Email me at mossberg@wsj.com. See video versions of my reviews at wsj.com/mossbergvideo.