Well, I was somewhat critical of the newest version of Firefox before, but I'd have to say that it really is growing on me. The fact that my extensions including the two "cannot live without" ones (Session Manager and All in One Gestures) have now been made to be FF 3.0 compatible.
I still haven't run into any real technical issues, although in spite of claims about improved memory usage, FF is still a pig when it comes to using memory (as I write this on my Windows XP machine it reports ~128MB of memory usage with 7 tabs open). Occasionally I get CPU usage spikes, but they're thankfully quite rare.
All-in-all it is working well.