My tips for vista64

Windows on Windows 32 (wow32) only allows 4gig for all the 32 bit apps. So why bother with more then 4 gig ?

Well anything not 32 bits can go sit above 4gig ie. random 64bit windows utils etc etc, As can file system cache. Which you can increase
eg. fsutil set memoryusage 2
So 6G will give slightly more memory to your wow sessions. And a big cache should give better performance.

Also use multiple hard drive and junctions/symlinks. But thats not really related to OS choice.