I just gave the demo a try and it was unplayable on a Athlon X2 4400, witha geForce 7800GTX, under Windows x64. Now this system should not have any problems play such a game even with everything turned up to the max, yet no matter the resolution of graphics detail level (ever try 640x480 with everything set to low?), the game pauses ever few seconds for about a second. This is not the systems fault as many other games such as Battlefield2, Area 51 and Farcry work without issue so it has to be the engine, but basicly I was very disapointed that it would have such issues on a top of the line rig. On my other rig running Windows XP 32bit, with an Athlon X2 4600 and a 7800 GT everything played fine, so I feel safe is saying that it is an XP x64 issue.
ERIC
ERIC