nope. We have some xp64 boxes at work and it's causing trouble all day. For example it's funny when my boss wants to install itunes for his ipod. The 32 bit installer says that this is a 64 bit operating system and that you should get the 64bit installer. No CD-Burning or ripping possible with iTunes. The 64 bit installer then says: "Sorry.. this installer works only on Vista64".
The problem is: xp64 needs special drivers. xp drivers are not working. vista drivers are not working. most manufacturer are not interested in creating drivers for it since there are still more people using windows nt then windows xp64. It won't even get the sp3 that was released for the 32bit edition.
Strange, I know plenty of people who have been running it for donkey's now with little to no problems, hardly something that can be said by everyone I know running Vista.
And come on, who on earth would actually want to use iTunes? :P