I don't know if anyone has posted this yet, don't think so, but Anandtech has posted a preview of the 64-Bit Windows Preview, including benchmarks.
http://www.anandtech.com/systems/showdoc.html?i=1961
"The actual performance under Windows XP 64-bit Preview showed great promise, but it is still something of a mixed bag. We were impressed that the CPU, Floating Point, and memory ALL showed performance improvement in XP64 compared to regular XP... We were also impressed with the 15%+ improvement in Media Encoding when running the same 32-bit encoding program under XP and XP64. Performance of current 32-bit games under SP64, however, was below expectations."
Anxiously awaiting yamhill....is it here yet?
http://www.anandtech.com/systems/showdoc.html?i=1961
"The actual performance under Windows XP 64-bit Preview showed great promise, but it is still something of a mixed bag. We were impressed that the CPU, Floating Point, and memory ALL showed performance improvement in XP64 compared to regular XP... We were also impressed with the 15%+ improvement in Media Encoding when running the same 32-bit encoding program under XP and XP64. Performance of current 32-bit games under SP64, however, was below expectations."
Anxiously awaiting yamhill....is it here yet?