Alright, average of 30 FPS during campaign intro, 25 at speech on carrier, "high" preset, 1280*960.
50-60% CPU usage on average, spikes to over 80% (up to 85%). Distributed over all 4 cores, but 1 or 2 seem to be taxed slightly more.
Q9550 (E0) @2.8GHz
4GB DDR2-800 5-5-5-15
P35 board
8800GTS 512
Can run again with CPU @ 3GHz, but it seems clear Arma 2 really needs those cores.
*Maybe a more powerfull graphics card could take away some load from the CPU, but I can't say how much good it would do you.