Some of the most rock solid theories to use software is to ALWAYS use the second-last major version of a product untill a new launches.
Say ... Windows Vista launched, but you still used Windows XP SP2 (x86).
Then, after a few years worth of updates, you can bet Windows Vista SP2 (x64) fully patched is faster, more stable and less prone to crashes/freezes, etc than Windows 7 at launch.
Repeat scenario for Windows 8. It just launched, good, it's a perfect time to start using Windows 7 SP1 x64.
The last doesn't mean the best. And it's been proven time and again.