Just to add a data point to the discussion. I just received a new laptop, onto which I installed 7068 x64 and 7700 x64 as an upgrade. Laptop specs at the end of the post. I noticed a speed up from 7068 to 7077, but 7077 seemed somewhat more unstable. I kept getting explorer error, where a notification would pop-up telling me that explorer had quit and was restarting.
I did a clean install of 7100 x64, and have had no problems. It is as fast as 7077, but no stability problems as of the install, which was Friday night PDT.
The Laptop is a MPC Micron T2500
Processor - T9300 (2.5 gHz) Core 2.
Chipset - Intel PM965
Memory - 4 GB DDR2-800
Video - nVidia 8600M GS - 256 MB
We'll see how it goes.