I currently run Vista 64 on my machine with 4 gigs of ram, while you may have issues with older hardware this is a new build and things work fine.

I get better performance under wow, lotro etc. then I do under XP and the 64 bit version of Vista runs smoother ie: snappier then the 32-bit version.

XP 64 on the other hand is a mess, it was an after thought that was hodge podged together from two different code bases and has no quality driver support. Vista on the other hand requires that 32-64 bit drivers are released together.

If you wish to discuss this further as I am rushing this post please let me know.