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.