If you load up on RAM you'll get a little more performance out of 64. I've been pleased with it overall.
My only gripe is that the video drivers for nVidia aren't always 64bit friendly.....and my TV card doesn't work in Vista64. I've noticed a lot of application crashes on BF2, for instance, and am guessing it's a video driver error that causes it to have memory errors....but it could be something else in the core OS. You may run into some hiccups, but overall, general web browsing and Microsoft Apps are pretty stable.