Firefox 3 beta 1 is great
I've been using the Firefox beta for a week now and I have to admit, it's a wholesale improvement over the 2.x branch. More stable, uses lower memory and the OS integration is much nicer, particularly on OSX with the default Proto theme. Works just as nice as Aranox's GrApple that I've been using.
Haven't really taken advantage of most of the newer features they've developed though do like the way they've added tagging to the bookmarking though I imagine it will be a little while before the Delicious bookmarking Add-On moves in line with it.
If anything, the one thing I'm noticing is how much of Firefox is the Extensions I've been putting into it. Finding myself having to work around some of the things that are not updated yet (Email This ! just updated today for example which was annoying not to have for a few days) and waiting for things like Delicious bookmarks, YSlow, Web Developer and Firebug to catch up).
It's nice though. Using it for all my main browsing now and it seems fast and responsive. Check it out if you're on OSX.