I've been running Firefox 4 (beta versions, now beta 11) and it's excellent, also very fast.
Edit: I'm now running the Beta12 'candidate' build. 25/Feb Beta 12 next week and RC soon after
The new layout with tabs on the top (Windows Aero) is a big improvement re: vertical screen space.
If you're not technical then stick with V3.6 for a few months until all your plugins are upgraded.
If you're a techie then go for it now! Use the Nightly tester Tools to override plugin compatibility.
The final release is due around the end of
For the early adopters, use the British dictionary as the Aussie one needs upgrading.
Install the FEBE plugin to backup your cookies, bookmarks, passwords etc.
Then uninstall Firefox 3.x (and delete all personal data)
Install Firefox 4
Install FEBE (the V7 beta that is Firefox 4 compatible)
Restore your bookmarks, cookies and passwords.
Install the other plugins you need
My plugin set:
1. Adblock Plus — Ads were yesterday!
2. British English Dictionary — British English Dictionary R1.19 for Firefox, Thunderbird and SeaMonkey by David Bartlett.
3. Color Inspector 3D — Shows all colors of an image in a rotatable RGB-color cube.
4. DOM Inspector — Inspects the structure and properties of a window and its contents.
5. DownThemAll! — The mass downloader for Firefox.
6. Exif Viewer — Extracts and displays the Exif (Exchangeable Image File), IPTC-NAA/IIM (International Press Telecommunications Council / Newspaper Association of America / Information Interchange Model), and IPTC Core (Adobe XMP, Extensible Metadata Platform) metadata, as stored by digital still cameras, in both local and remote JPEG images.
7. FEBE — Backup your Firefox data
8. Firebug — Web Development Evolved.
9. FxIF — View EXIF data in image properties
10. Histogram Viewer — Generates the histogram of a selected image.
11. IE View — Open pages in IE via Firefox menus
12. Net Usage Item — Displays your internet usage on the toolbar.
13. Nightly Tester Tools — Useful tools for the nightly tester.
14. SQLite Manager — Manage any SQLite database on your computer
15. Tab Mix Plus — Tab browsing with an added boost.
16. ViewSourceWith — View page source with external application
17. Web Developer — Adds a menu and a toolbar with various web developer tools.
18. deskCut — Create desktop shortcuts from the context-menu. Windows, Linux and Mac supported.