It's overall very nice. It's a little faster than 1.5 I think, and there's some nice new features. However, one thing I DO NOT like is the new visual style. It's very boring and looks horrible beside other browsers like Safari, or even IE7. Prime suspects include the horrible green "Go" button beside the address bar.
I also don't like the fact that the drop down tab list is there ALL THE TIME, as opposed to only there when there is too many tabs to keep on the screen.
Memory usage seems fine, although to be fair I've never experienced any of the memory leak issues everyone else seems to have. I've never seen mines go over 60,000k, but then again I usually only keep a few tabs open at the one time, no extensions either.