I use it, with only a couple issues:
1. Haven't found any drivers for my Canon ip1500 (so now it's connected to laptop).
2. Lack of Virtual CD mounting software. I know Daemon Tools has an x64 version out, but it fails to install on my x64 machine. Workaround: don't be lazy and actually put the CD in the drive.
Granted I also don't have much software that's actually 64-bit at this point, so x64 isn't really providing me much benefit. I do have 3 GB RAM, so with x64 one application should be able to address > 2 GB. Again, not very useful at this point since I don't really run anything that uses that much RAM (I do run some apps that come close, so at least I'm somewhat future proof).
I installed it, it works for pretty much everything I do, so I have never seen a reason to go back to 32-bit XP.