iTunes 7.6 is out, with x64 support at last! Just as I predicted 
http://www.apple.com/itunes/download/
It redirects you based on your OS. Or download the 32-bit one here and the 64-bit one here.
Update: Sadly it isn’t actually a 64-bit binary. Lame, but what do you expect from Apple, who seem to be pretty stuck in a 32-bit world. At least it includes a 64-bit iPhone / iPod Touch driver, which is all that was really needed.
