Oh, and a must have extension for those who want to enjoy the 2.0 release: Nightly Test Tools. Despite it's geeky sounding, "why the hell would I need that?" name, it is essential for preventing your transition from Firefox 1.5 (or lower, god forbid) to Firefox 2.0 from becoming an exercise in frustration caused by extensions being disabled if the authors have not updated them for Firefox 2.0. With Nightly Tester Tools, you can "Make compatible" any "outdated" extensions to force them to be usable in Firefox 2.0. Granted, this doesn't always work (if, say, an extension uses functionality that no longer exists in Firefox 2.0), but for most of the extensions I've had to "make compatible" so far function just fine.
Oh and while you're there playing with your extensions (Firefox extensions you sicko), you'll probably find that you no longer need extensions that save and restore your browsing session (such as SessionSaver or the functionality that comes with Tab Mix Plus) and certain feed subscription extensions (such as Feed Your Reader) - these already come built into Firefox 2.0.