Cant add much to this really, i have used Windows 7 only in VMWare for around 18 months now as i got it via MSDN, and have had several builds either via MSDN or via Uni.
I can say that in VMWare it runs better than Vista and Vista SP1 (Business), but not as good as server 2008.
I dont expect anything to run well in a virtual machine, but its good to compare, and use a few benchmark tools.
XP is still a clear winner as i dont give stuff about the visual design, if i did i would get a MAC for sure.
Vista is a little more security aware, but nothing you cant add to XP with a few bits of light software.
I have only used X86 or 32Bit one, so maybe the 64Bit version is just amazing and super quick.
If so, i can feel a notebook upgrade coming, even though i swore my next notebook would be a MacPro15"