will run very nicely, only thing is not everything supports 64 bit at the moment, including drivers for a some hardware. Best thing to do is to search for all your needed drivers in 64 bit versions, if they are all available then go for it
I wouldnt go with XP x64, i've tried it and there are too many driver problems. Unless you can find out if all your hardware has 64-bit versions, i wouldnt get it.
I was going to get it, but its just not worth it at this time unless its for your business. If its your common PC for gaming and browsing and such, wont make much of a difference, just wait for Vista and run pro til then.