Firefox 3 in two words: It's fast.

Before releasing Firefox 3 on Tuesday, Firefox's developers fixed memory leaks and bugs that slowed down Firefox 2. And the developers added lots of little timesaving features to streamline usage. The designers paid particular attention to tools that make it easier to identify favorite Web sites, and return to them over and over.

But the news isn't all good. Firefox 3's developers, Mozilla.org, brag about new security features designed to protect users against phishing and sites that attempt to download malware. But the new features are unreliable, and will likely lull naive users into a false sense of security. The potential damage is limited there -- even moderately expert users shouldn't have a problem because they don't need the warnings. But from a security standpoint, Firefox 3 is a step backward.

Firefox 3 speeds up browsing by reducing memory usage, and it has user interface changes that make it easier to get to where you're going.
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The biggest changes in Firefox 3 are under the hood. Mozilla developers plugged memory holes that were causing earlier versions of Firefox to use more and more memory over time, until the browser slowed down the entire system and crashed it entirely.

Those problems have pretty much been eliminated with Firefox 3. I've been using Firefox 3 pre-release versions (reviewed here) as my primary browser since December, and it's crashed a couple of times total during recent months. That's compared with crashes a couple of times a week with Firefox 2.

The most useful new feature in Firefox 3: You can now zoom an entire Web page. Previous versions of Firefox only let you zoom the text, which eventually meant the text was going to start overlapping with other element on the page. With Firefox 3, the entire page zooms in and out, with the graphics, interactive elements, text, and layout all remaining in proportion to one another.

Firefox 3 also remembers the zoom setting for any site you visit, and returns to that setting when you return to any page on the site.

Changes to the location bar are much more significant. It has a nickname now: The Awesome Bar (and that's an awesome nickname). It looks the same, but the behavior is different. When you start typing into the Awesome Bar, Firefox starts searching through your browsing history and bookmarks. The Awesome bar shows you a dropdown menu of pages, and when you see the page you want, you can just arrow or mouse down and select it.

Previous versions of Firefox had a rudimentary version of that kind of search, but the search was limited to the URL and title of a page, and the letters you typed had to be at the beginning of the page URL.

The Awesome Bar weights its search results by an algorithm Mozilla.org calles "frecency" (another awesome word). The searches are weighted to favor frequently-visited pages and pages you visited more recently.

For more details, Dria.org has a good overview of the Awesome Bar and how it works.

I love the Awesome Bar, but some users of Firefox test versions hated it. If you hate it, you can disable it by installing the oldbar add-on to Firefox.