Well that one guy had a Athlon X2 4800 and just a geforce 8800 GTS 320mb, all stock, not OCed and he got 8200, the geforce 8800 GTS 640mb on their tests with a X6800 only got 8830!?!?
Its possible that the rest of the system wasn't considered.
For example, all of the following items can affect a score. (Not limited to of course)
Room Temp
CPU temp
Mobo temp and chipset temps
Amount of RAM and timmings (And it voltage)
Amount of running processes
Amount of OS Tweakage ( pretaining to memory and pagefile)
The list goes on and on.. Point is, unless we know exactly every aspect of the systems, we can't really pin down why the scores are such.