This may not be a bug with the x64 release per say, but
When running the install program off the boot CD, I set my windows partition to 15270 (15200 was the minimum size it said the partition could be). But everything I hit okay the partition is set at 15274. Swap area i set to 1024 (i have 3GB onboard ram) and it sets it at 1019.
Somewhere along the way calculations are getting messed up, either on the interface (one is using base 1000 and the other is using base 1024) or it's adding those extra 4mbs for some reason I can't comprehend.