The newer version of Firefox from Mozilla is definitely better than Firefox 3.6 and is definitely worth trying out. Firefox 4 runs on the Gecko 2.0 web platform. Earlier today I downloaded Firefox 4 and put it through some drills, here is a review of Firefox 4 Beta 1 where you can find the new features and also the how Firefox 4 fares against other browsers in web browser benchmarks.
New User Interface
Firefox 4 sports a completely different interface, some of which are from Opera and Google Chrome. Firefox 4 has some new buttons and also a unified menu which is similar to the one Opera 10.6 has. In addition to that the tabs also default to the top which is similar to Google Chrome.
However, the menu bar is initially hidden and users can unhide it to go back to the older navigation found in Firefox 3.6 and below.
New Add-ons Manager
Firefox 4 sports a new add-ons manager which integrates into the browser. However, the interface is still under construction and you cannot use the add-ons manager to browse and install add-ons yet. However, it is definitely much better than the earlier version and also has some new developer tools.
Mozilla also says that the add-ons manager UI will be changed before the final release, so donâ€™t start falling in love with it yet.
Search and Switch to Open Tabs
Firefox 4 also has a hidden gem in the smart location bar, which will allow you to switch to an open URL by typing in the URL or searching for the title of the page. The feature is very handy if you have several open tabs and want to switch to it without navigating through all the tabs.
When you want to switch to an open tab, just start typing the URL or the title of the page and you will be shown an option to Switch to that open tab. Pretty neat.
Windows 7 Integration
Firefox 4 tightly integrates into Windows 7 by having tab previews and Jumplists. Using the tab previews you can easily preview all open tabs. In addition to that the jumplists allows you to quickly perform tasks and open frequently opened URLs.
Native HTML5 WebM Videos Support
Firefox 4 has native support for HTML5 WebM videos. WebM is an open source royalty free codec for HTML5 videos which is an alternative to H.264 and Theora codes (Learn more about WebM). In my tests HTML5 videos works pretty good on YouTube.
Speed and Other Benchmarks
Firefox 4 is definitely much more lighter and faster than Firefox 3.6 and it uses much less memory than the earlier versions. However, Firefox 4 is not yet the fastest browser and it was beaten by both Google Chrome 6 (dev) and Opera 10.60 in the Peacekeeper benchmarks I ran.
Firefox 4 also has Crash protection for Flash, QuickTime and other plugins, however, this was introduced in Firefox 3.6. Firefox 4 also has a HTML5 parser which allows you to run the latest apps, support for WebSockets for real-time online interactions like chatting and gaming and IndexedDB which will allow users to use offline storage.
If you have not yet downloaded Firefox 4 Beta 1, you can do it from here or visit this blog post on Mozilla to find out all the latest features available in Firefox 4.