But just how good is Chrome? How does it differ from IE and from less popular, but still important, browsers like Mozilla’s Firefox and Apple’s Safari?

I’ve been testing Chrome for about a week, trying out all its features and using it side by side with Microsoft’s latest iteration of IE, which came out just last week.

My verdict: Chrome is a smart, innovative browser that, in many common scenarios, will make using the Web faster, easier and less frustrating. But this first version — which is just a beta, or test, release — is rough around the edges and lacks some common browser features Google plans to add later. These omissions include a way to manage bookmarks, a command for emailing links and pages directly from the browser, and even a progress bar to show how much of a Web page has loaded.

Chrome’s interface has some bold changes from the standard browser design. These new features enhance the Web experience, but they will require some adjustment on the part of users. For instance, Chrome does away with most menus and toolbar icons to give maximum screen space for the Web pages themselves. Also, Google has merged the address bar, where you type in Web addresses, with the search box, where you type in search terms. This unified feature is called the Omnibox.

One striking difference in Chrome is how it handles tabs, which display a single Web page. In Chrome, each tab behaves as a separate browser. The bookmarks bar, Omnibox, menus and toolbar icons are located inside the tab, rather than atop the entire browser. The tabs appear at the top of the computer screen. Chrome also groups related tabs. If you open a new tab from a link in a page that’s already open, that new tab appears next to the originating page, rather than at the end of the row of tabs.

Despite Google’s claims that Chrome is fast, it was notably slower in my tests at the common task of launching Web pages than either Firefox or Safari. However, it proved faster than the latest version of IE — also a beta version — called IE8.

Meanwhile, Microsoft hasn’t been sitting still. The second beta version of IE8 is the best edition of Internet Explorer in years. It is packed with new features of its own, some of which are similar to those in Chrome, and some of which, in my view, top Chrome’s features.

Google’s Chrome browser displays thumbnails of a user’s most-visited pages when a new tab is opened, rather than a blank page.

For example, while IE8 also groups related tabs, it assigns a different color to each such tab group and allows you to close them all with one click. It has a “smart” address box of its own, that drops down a list of suggestions as you type, though it retains a separate search box.

IE8 also has breakthrough privacy features that exceed Chrome’s, and includes a new technology called Accelerators, which allows you to take rapid action on any selected word or phrase on a Web page, such as generating a map for a place name, without switching to a new page.

As they develop, each of these browsers has a good chance of besting Firefox 3.0, which I have regarded as the best Web browser for Windows, the only operating system on which Chrome currently runs. But they will have to get faster at loading pages. And, to best Firefox on the Macintosh, Google will have to make good on its promise to produce a Mac version of Chrome, something it says it will do in the coming months. Microsoft has no plans to produce a Mac version of IE8.

Chrome and IE8 are far more advanced than Apple’s Safari. Safari is speedy on both Mac and Windows platforms, but lacks many of the key intelligent features of its newer Google and Microsoft rivals.

Why is Google igniting a new browser war? There are two main reasons, and both involve competing with Microsoft. First, the search giant fears that because its search engine and other major products depend on the browser, Microsoft — with its rival online products — might be able to gain an advantage by altering the design of IE, which has roughly a 75% market share.

Second, and more important, Google sees the Web as a platform for the software programs, or applications, that currently run directly on computer operating systems, notably Microsoft’s Windows. It says current browsers lack the underlying architecture to enable future, more powerful Web applications that will rely more heavily on a common Web programming language called JavaScript. Chrome was designed to be the world’s speediest browser at handling JavaScript.

That move might one day make Chrome a sort of online operating system that competes with Windows. “Think of Chrome as more than a simple Web browser,” Google declares. “It’s a platform for running Web applications.”

Microsoft’s IE8 has an “Accelerator” feature that lets users select any Web text and then map, translate, search or email their selection without leaving the page.

I tested Chrome, and IE8, on a plain-vanilla Lenovo ThinkPad laptop running Windows XP, and equipped with a modest processor and one gigabyte of memory.

To gauge Chrome’s speed at loading Web pages, I launched two large groups of typical Web pages simultaneously, each site opening in its own tab. One group included 15 sports sites, the second 19 news sites. In both tests, Chrome’s speed fell in the middle, at 35 and 44 seconds, respectively. IE8 was slower, taking 49 and 75 seconds to open the two groups of sites. But Firefox and Safari were much faster, notching identical speeds of 19 seconds for the 15 sites and 28 seconds for the 19 sites.

Google claims that future, more sophisticated Web applications relying more heavily on JavaScript than today’s sites do would run faster on Chrome. Of course, I couldn’t test any claim about future scenarios, but I did run Chrome on several JavaScript test sites, used by developers. It handily beat the other browsers. However, Google doesn’t claim users would see much difference on current Web application sites.

I also tested Chrome’s compatibility with scores of common Web sites. In general, it did well, rendering the sites properly. But I ran into problems with video. Some video sites refused to recognize Chrome, because its development has been a secret. On others, like Major League Baseball’s site, videos mostly played properly, but sometimes didn’t.

IE8 also has some compatibility issues, for different reasons. It’s the first version of Internet Explorer to hew closely to Web standards. Earlier versions used some nonstandard ways of rendering Web sites, prompting some site designers to adopt techniques that made their pages work in IE, but look odd in Firefox and Safari. Now, ironically, these pages also look strange in IE8. So Microsoft was forced to build in a special Compatibility View button that users must click to see the sites properly.

Chrome is built on three core design principles. The first is its spare user interface: just two menus and a handful of toolbar icons. IE introduced a similar approach in its version 7, but with a difference. Microsoft allows users to restore a traditional menu bar; Google doesn’t. The only toolbar icon you can add in Chrome is a Home button.

The second principle is that a user can type anything into a single place, the Omnibox, and instantly get suggestions on where to go, gleaned from the user’s own browsing history and Google’s rankings of popular sites. Whether you type in a Web address or a search term, the Omnibox is very smart. In my tests, it sometimes came up with the right destination after I typed only one or two letters of the name of a site I often visited.

The Omnibox has another cool feature: Tab-to-Search. If you type in the name of another site that includes its own search feature, like Amazon.com, the Omnibox lets you just press the tab key to search within that site, without opening it first. Chrome, through its Options settings, also lets you change the default search engine used by the Omnibox. Instead of Google’s own search service, you can use Microsoft’s Live search, Yahoo search, or others.

The third big principle behind Chrome is that each tab runs, under the hood, as a separate browser. Tabs can be dragged off the main browser and turned into separate windows. If one tab crashes, the rest of the browser keeps running. But this doesn’t work perfectly. In my tests, all of Chrome died on me when I tried watching an Olympics video on the NBC site.

You can even make a tab a standalone application that runs from the Start Menu, or the desktop, as if it was a separate program.

Chrome has a few other key features. When you open a new tab, you don’t get a blank page, but a set of thumbnails for your most-visited pages, plus lists of recent search engines you’ve used, recently used bookmarks and recently closed tabs.

Like other browsers, Chrome puts up a warning when you try to visit a malicious or phony Web site, and it has a private browsing mode, called Incognito, which allows you to browse without leaving any history on your computer — a feature popularized in Safari.

Chrome also has a pop-up blocker, but it’s annoying because it flashes a notice that a pop-up has been blocked. IE also does this, but unlike in Chrome, the warnings are much less intrusive.

Internet Explorer 8 has some new features Chrome lacks. Its private browsing mode, called InPrivate, is the first I’ve seen that not only leaves no traces on your own computer, but also bars Web sites from collecting some types of information on where you’ve previously been surfing.

While IE8’s address box and search box remain separate, each also offers rapid suggestions; and both are organized better than Chrome’s. For instance, the suggestions that drop down from its address bar are divided neatly into categories drawn from the browser’s own guess, your history and your favorites. One downside: For this to work in Windows XP, you must first install Microsoft’s desktop search product.

Like Chrome, IE8 lets you switch your default search provider, but it also allows you to switch search engines on the fly. When you type in a search term, icons for alternate search engines appear at the bottom of the suggestion list, and you need only click on these to see search results from, say, Google, instead of Microsoft’s own Live search engine.

IE8’s Accelerators feature presents a blue-arrow icon above any text on a Web page that you have selected. Clicking on the icon brings up a list of actions you can take using the selected text, such as posting it to a blog, emailing it, mapping it or searching it. While these actions are set by default to use Microsoft’s own Web services, you can change them to use Google’s, Yahoo’s, or those from other companies.

Microsoft also has built in a feature called Web Slices. These are portions of a Web site that a site developer can designate to appear in the IE8 Favorites bar and to constantly update themselves. An example might be bidding on eBay.

Like Chrome, IE8 also displays useful information whenever you create a new tab, including a list of recently closed tabs and a list of Accelerators.

With the emergence of Chrome, consumers have a new and innovative browser choice, and with IE8, the new browser war is sure to be a worthy contest.

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

On Friday, Apple (AAPL) is launching a second-generation iPhone, called the iPhone 3G, which addresses both of those problems, while retaining the look and feel of the first model’s hardware and software.

The base version of the new iPhone costs $199 — half the $399 price of its predecessor; the higher-capacity version is now $299, down from $499. Yet, this new iPhone is much, much faster at fetching data over cellphone networks because it uses a speedy cellular technology called 3G. And it now sports a GPS chip for better location sensing.

The company also is rolling out the second generation of its iPhone operating system, with some nice new features, including wireless synchronization with corporate email, calendars and address books. And there’s a new online store for third-party iPhone programs that Apple hopes will make the device usable for a wider variety of tasks, including gaming and productivity applications. This new software and store will also be available on older iPhones, through a free upgrade.

I’ve been testing the iPhone 3G for a couple of weeks, and have found that it mostly keeps its promises. In particular, I found that doing email and surfing the Internet typically was between three and five times as fast using AT&T’s 3G network as it was with the older AT&T network to which the first iPhone was limited.

Apple’s new iPhone operating system includes an ‘App store,’ where you can browse for, and download, third-party software.

The iPhone 3G is hardly the first phone to run on 3G networks, and it still costs more than some of its competitors. But overall, I found it to be a more capable version of an already excellent device. And now that it’s open to third-party programs, the iPhone has a chance to become a true computing platform with wide versatility.

There are two big hidden costs to the new iPhone’s faster speed and lower price tag. First, in my tests, the iPhone 3G’s battery was drained much more quickly in a typical day of use than the battery on the original iPhone, due to the higher power demands of 3G networks. This is an especially significant problem because, unlike most other smart phones, the iPhone has a sealed battery that can’t be replaced with a spare.

Second, Apple’s exclusive carrier in the U.S., AT&T Inc. (T), has effectively negated the iPhone’s up-front price cut by jacking up its monthly fee for unlimited data use by $10. Over the course of the two-year contract you must sign to get the lower hardware prices, that adds $240, overwhelming the $200 savings on the phone itself. If you want text messaging, the cost rises further. With the first iPhone, 200 text messages a month came free. Now, 200 messages will cost $5 a month, or another $120 over the two-year contract.

The iPhone 3G still has a couple of features that made the first version unpalatable to some potential buyers. It uses a virtual on-screen keyboard instead of a physical one. While I find the virtual keyboard easy and accurate, not everyone does. Also, in the U.S. and in many other countries, the iPhone is still tied to a single exclusive carrier, whose coverage or rate plans may be unacceptable to some.

Here is a rundown of the changes in the new model.

Design: The new iPhone looks almost exactly like the old one. It is the same length and width, has the same big, vivid screen, and has the same number and layout of buttons. The main difference is the back, which is now plastic instead of mostly metal and curved instead of flat. It’s very slightly thicker in the middle, with tapered edges, and weighs a tiny bit less.

The new iPhone 3G (left) delivers much higher Internet download speeds over cellular networks than the original iPhone (right).

Like its predecessor, the iPhone 3G comes in two models distinguished only by storage capacity: 8 gigabytes and 16 gigabytes. The top model is available in black or white.

Apple has greatly improved the audio on the new iPhone. I found the speaker was much louder, for music and for the speakerphone. But the new phone produced an echo when used with the built-in Bluetooth system in my car. Also, the headphone jack is now flush with the case instead of recessed as on the first model, so it can accept any standard stereo earphones.

The camera, however, is still bare-bones. It can’t record video and has a resolution of just two megapixels. The power adapter is now tiny, at least in the U.S., but Apple no longer includes a dock for charging, just a cable.

Software: The basic software is similar. The biggest addition for some users will be full compatibility with Microsoft’s (MSFT) widely used Exchange ActiveSync service, which many corporations use. In my tests, I was able to connect the iPhone 3G to my company’s Exchange servers in a few minutes, and my corporate email, calendar and contacts were replicated on the phone. Any changes I made on the iPhone were reflected almost instantly in Microsoft Outlook on my company PC, and vice versa. Email was pushed to the phone as soon as it was received on the company’s servers.

One drawback: While you can have both personal and Exchange email accounts on the new iPhone, if you synchronize with Exchange calendars and contacts, your personal calendar and contacts are erased.

The new iPhone and upgraded older iPhones also will be able to use a new Apple consumer service, MobileMe, which offers synchronized push email, calendars, photos and contacts.

There are other improvements. You can now delete multiple emails at once, set parental controls and search your contacts. You can also save photos in emails or from Web sites. You can also now open Microsoft PowerPoint files sent as attachments, though I found in my tests that opening larger PowerPoint files crashed the phone.

Some software features missing from the first iPhone are still AWOL on the new one. There’s no copy and paste function, no universal search, no instant messaging and no MMS for sending photos quickly between phones.

Network: Like the old iPhone, the new one can perform Internet tasks using either Wi-Fi wireless networking or the cellphone networks. But the addition of 3G cellular capability makes the new model more useful for Web surfing, email and other data tasks when you’re not in Wi-Fi range. In my tests, in Washington and New York, I got data speeds mostly ranging between 200 and 500 kilobits per second. By comparison, the original iPhone, tested in the same spots at the same time, mostly got cellular data speeds between 70 and 150 kbps on AT&T’s old EDGE network. The new iPhone typically was between three and five times as fast as the old one.

While AT&T now has 3G networks in 280 U.S. cities, and aims to be in 350 by year end, it is converting its cellphone towers gradually, so not all areas of included cities have 3G coverage. The new iPhone falls back to EDGE speeds when 3G isn’t present.

One side benefit to 3G is that in some areas, voice coverage improves. At my neighborhood shopping center, where the first iPhone got little or no AT&T service, the iPhone 3G registered strong coverage. But I still found that calls regularly broke up on some major streets. In New York City, riding in a taxi along the Hudson, one important call was dropped three times on the new iPhone. Finally, I borrowed a cheap Verizon (VZ) phone and got perfect reception.

Battery life: Apple claims that over 3G, the new iPhone can get five hours of talk time, or five hours of Internet use. Talk time is twice as long on the older EDGE network, and Internet time is an hour better with Wi-Fi.

I ran my own battery tests using the phone’s 3G capability. Although I left the Wi-Fi function on, I didn’t connect it to a network, so the phone had to rely on 3G. In my test of voice calling, I got 4 hours and 27 minutes, short of Apple’s maximum claim and nearly three hours less than what I recorded in the same test last year on the original iPhone. In my test of Internet use over 3G, I got 5 hours and 49 minutes, better than Apple’s claim, but far short of the nine hours I got using Wi-Fi in last year’s tests.

More important, in daily use, I found the battery indicator on the new 3G model slipping below 20% by early afternoon or midafternoon on some days, and it entirely ran out of juice on one day. I overcame this problem by learning to use Wi-Fi instead of 3G whenever possible, turning down the screen brightness and even turning off 3G altogether, which the phone permits.

The iPhone 3G’s battery life is comparable to, or better than, that of some other 3G competitors. But they have replaceable batteries. The iPhone doesn’t.

Third-party software: If things go as Apple hopes, third-party software could be the biggest attraction to the new iPhone 3G, and to upgraded older iPhones. By some estimates, there will be hundreds of these programs, some free and some paid, almost immediately.

Apple didn’t supply me with programs for testing, but I managed to try several on older devices upgraded to the new operating system. I tested a game that used the phone’s motion sensors to control the action, and I tested several programs from America Online (TWX), including AOL Instant Messenger; AOL Radio, which streams music from the Internet; and AOL’s Truveo video search engine. All worked very well.

Among the programs Apple has publicly previewed were a sales automation program from Salesforce.com, a game called Super Monkey Ball from Sega and a program for bidding on eBay (EBAY). Also made public were a news reader from the Associated Press, a program for following live games from Major League Baseball and several programs for doctors, including the Epocrates drug reference.

Bottom line: If you’ve been waiting to buy an iPhone until it dropped in price, or ran on faster cell networks, you might want to take the plunge, if you can live with the higher service costs and the weaker battery life. The same goes for those with existing iPhones who love the device but crave faster cellular data speeds. But if you already own an iPhone, and can usually use Wi-Fi for data, you probably should hold off and get the free software upgrade before deciding whether it’s worth getting the new hardware.

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