Firefox 3 is close to being released (it is in beta now). Here is a nice screencast on new features. When I recently upgrade my Ubuntu it automatically installed the Firefox 3 beta (which I must say I don't really think was the greatest - asking would have been better). But for that reason, I have been using it and I like it. The menu bar improvements can actually be annoying in some ways but the advantages outweigh the problems with that feature, I think.
One very annoying thing with Firefox 3 is the Google toolbar is blocked. It doesn't comply with some new upgrade rule I think. Still I don't understand why they won't let me use the toolbar if I want (the message seems to indicate it is not a problem of incompatibility with Firefox 3 but not following some rule for how upgrades should be done. A number of plug-in have this problem but that is the only one that I really care about. I surprised Google hasn't made this work - even though it is still in beta since it is very close (weeks?) until the release.