Linux on netbooks isn’t going away though. In fact, software and hardware companies have been making big investments to improve Linux netbooks. For the past week, I’ve been using several flavors of Linux running on netbooks — Ubuntu, Hewlett-Packard’s Mi (which is based on Ubuntu) and Moblin, created largely by Intel and not yet available commercially. In all cases, the Linux netbooks failed at some basic functions that any laptop, no matter how tiny and inexpensive, should be able to handle, like working with printers. At the same time, Mi and Moblin have impressive graphical user interfaces well-suited to the habits of typical netbook users, like checking email and accessing social-networking sites, as well as the small screens and low horsepower of tiny laptops. In addition to Linux, all of the computers shared the standard features, or lack thereof, common among netbooks, including compact keyboards and no DVD drives.

H-P’s Mini 110 Mi Edition

The most polished of the products was H-P’s Mini 110 Mi Edition, a new model with a 10.1-inch screen that H-P will begin selling on its Web site for $279.99 on June 10. That’s nearly $50 less than what H-P will charge for the Mini 110 running Windows XP, which will come with a 160-gigabyte hard drive instead of the 8-gigabyte solid-state drive that will come with the Mi edition.

The striking thing about this netbook is the slick graphical user interface created by H-P that runs on top of Ubuntu and first began appearing on H-P netbooks early this year. Instead of a traditional desktop like that found in Windows and the Mac, Mi (pronounced “me”) arranges commonly used applications and content on a screen called the “dashboard,” which looks like a personalized Web page and lists recently received emails, fresh thumbnail images of favorite Web sites, and a Web-search toolbar.

The Mi home screen is a clever way to make the computer seem alive with on- and off-line content, which is fitting since netbooks are designed for on-the-go Internet activities. It’s also tailor-made for the small screen size of netbooks.

A more eye-catching iteration of Linux is Moblin, which I tried out in test form on an Acer netbook; it is expected to ship on netbooks by the end of the year. Moblin has a menu of icons at the top of the screen, the most interesting of which leads to the M-Zone, a home screen that displays calendar appointments and favorite applications alongside snapshots of recently visited sites and a continuous feed from the user’s Twitter network.

An icon called “People” leads to a list of instant-messaging buddies, while another, called “Zones,” let me organize all the applications I had launched into different virtual workspaces, which is useful for hopping between various tasks on a small-screen device like a netbook.

The look and feel of the standard Ubuntu system, without the Mi interface, is more commonplace. I tried out a Dell Mini 10 with a 10.1-inch display and 160-gigabyte hard drive that sells for $349 on Dell’s Web site. The Mini 10 ships with version 8.04 of Ubuntu, which resembles Windows XP, with its desktop, taskbar and pop-up menu system. Ubuntu, in some cases, seemed to overestimate the size of the Dell Mini’s display: A window for configuring wireless-networking capabilities was so large it bled off the screen, and I couldn’t access all the buttons on it. I also installed on the Dell a new version of Ubuntu Netbook Remix, which works better on small screens. Since a Windows XP version of the Dell Mini 10 sells for the same price as the Ubuntu, I can’t see a compelling reason to choose the Ubuntu option.

All the netbooks I tried had compatibility problems with other external devices. The netbooks couldn’t load the software drivers to let me print to my Canon and Dell printers. I couldn’t load pictures over a USB cable from my Canon PowerShot SD750 digital camera. I was able to get my pictures on the machines by plugging a storage card from my camera directly into the netbooks.

Canonical, the London company that oversees development work on Ubuntu, says it is improving the system’s compatibility with various devices. Intel says it is unfair to judge Moblin until it is commercially available.

Some key applications currently don’t run on Linux, like Apple’s iTunes, which makes it difficult to load music files onto iPods from the netbooks. While the Linux laptops didn’t run Microsoft Office, they came with OpenOffice, a free package of word-processing, spreadsheet and presentation applications that allowed me to open and modify basic Word and Excel files.

The companies behind Linux netbooks have made great strides in improving user interfaces, but until they can achieve similar breakthroughs in how the machines work with other devices, Windows netbooks are still a better deal.

• Email nick.wingfield@wsj.com. Walter S. Mossberg is away and will return next Thursday.

That is the question that Mozilla, the nonprofit organization that makes the leading alternative browser, hopes to answer this month when it releases version 3.0 of its Firefox Web browser. In some tech-industry circles, Firefox already is preferred over Microsoft’s (MSFT) Internet Explorer and Apple’s (AAPL) Safari, but it still isn’t used by most people, and Mozilla is hoping to broaden its appeal.

The new version will be released simultaneously for Windows and the Mac’s OS X operating system, as well as for Linux. While each of the three editions will have the visual style of the operating system on which it runs, all three will have the same features.

I’ve been using prerelease versions of Firefox 3.0 for months, and have recently been testing a near-final version and comparing it closely to IE and to Safari. I have tested it on multiple Windows PCs and Macs, on desktops and laptops, over slow connections and fast ones. I have tried it with well over 100 Web sites.

My verdict is that Firefox 3.0 is the best Web browser out there right now, and that it tops the current versions of both IE and Safari in features, speed and security. It is easy to install and easy to use, even for a mainstream, non-technical user. It can be downloaded, free, at mozilla.com by clicking on “Firefox 3 Sneak Peek.”

This situation may change. Microsoft is working on a new version of IE, scheduled to be unveiled later this year, with some impressive new features. And Apple is always working on new iterations of Safari, though it is secretive and hasn’t disclosed its plans. But for now, in my view, Firefox 3.0 rules on both Windows and Mac.

I couldn’t find any significant downsides to Firefox 3.0. Every page I tried rendered properly and rapidly on both platforms. I ran into only one glitch, in a preference setting. That problem appeared on only one of my four test machines and was fixable with the help of Mozilla, albeit via a geeky method.

In the one or two cases where Firefox lacked a feature I thought important, such as the “auto fill” feature in Safari that can quickly fill out an online form, I was able to find an add-on that did the trick from Mozilla’s vast library of add-ons, which are written by people all over the world. (One caution: Some existing add-ons won’t work with the new version until their authors update them.)

When Firefox first came out, it was the fastest browser, but it lost that title over the years. However, in my tests, this new third version of Firefox regained the speed crown. It beat IE 7 handily on my test Windows computers and edged Safari slightly on my test Macs.

For example, using a new Dell (DELL) XPS One desktop, I opened identical folders containing the same 16 bookmarks on both IE 7 and Firefox 3.0. IE took 37 seconds to completely display the 16 pages, but the new Firefox did it in just 23 seconds. On a new Apple iMac, I did a similar, but more daunting, test — opening identical folders containing 24 bookmarks. Safari rendered all of the pages in 36 seconds, but the new Firefox finished the job in 32 seconds.

The latest Firefox has a number of new and improved features. If you type any word or phrase into its address bar, the browser instantly searches your history and bookmarks for a possible match, to save you from typing or combing through your bookmark list.

The whole process of managing bookmarks has been vastly simplified. Every Web address is accompanied by a star icon at the right. To bookmark the site, you just click the star once. No other action is required. To specify where to file the bookmark, you click the star twice. You also can remove bookmarks by clicking the star. And you can tag bookmarks with key words, to make it easier to find them.

There are also smart bookmark folders, which gather your most visited sites, or most recently bookmarked sites, automatically into folders. You also now can more easily back up and restore your bookmarks, complete with tags.

Security is also improved. The old version of Firefox would warn you when a site you were visiting appeared to be a fake, designed to steal your identity. (IE has a similar feature, though Safari doesn’t.) But Firefox 3.0 now warns you about sites that are known for trying to plant viruses, spyware and other malicious software on your computer, a warning the other big browsers don’t yet provide.

With one click, Firefox 3.0 also provides details about who owns the site you’re visiting, and whether it’s encrypted, if the site owner has adopted a special type of security certificate.

My bottom line: Even though you already have a built-in browser, Firefox 3.0 can improve your Web experience.

• 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.