WEI is just a number, it chages slightly every time it is run.
Changes every time it is run? Ummm, nope! Shouldn't do that. Not unless some hardware change occurred. Note that WEI disables any throttle down power saving features.
Hi blair. Do I know you from somewhere else? Perhaps a different blair.
Note that Vista and Win7 WEI have different scale caps. With Vista, 5.9 was the highest you could get. This ceiling was hit often as hardware technology advanced over the next couple years after Vista's release. Win7 is designed to take advantage of the new hardware advances since Vista so the ceiling was raised to 7.9. Your HW was probably always capable of 6.4, but was capped by Vista's 5.9 ceiling. It does not get a higher score because of how Win7 runs, as it runs the same way - only the cap has been changed.
We are already seeing some power users hitting the high 7s for graphics, CPU, and RAM. It is likely MS will raise the 7.9 ceiling again as hardware technologies improve.
HD performance currently caps at 5.9, unless using SSDs, or RAID0 with high-end drives. The cap for HDs may be changed sooner (I hope) because currently, if you have a nice 7200RPM drive with 32Mb buffer, you will hit 5.9. But if you have a 10,000RPM drive with a 32Mb buffer, you still only get 5.9. My HTPC with a 1.5Tb 5400RPM drive gets 5.9. Two 10K in RAID0 (striped) raises it a little - to low 6s. I have seen one WEI with 7.7 for the HD score, but he was using two SSDs in a RAID0 array.
Here's mine, and I don't have top of the line stuff.