My Specs:

CPU- Intel i5 3450 stock @ 3.1GHz
GPU- 2x Nvidia 670s in SLI, factory overclocked EVGA (FTW Edition)
MEM- 8GB 1333MHz PC3 10600 @ stock clocks
SSD- Intel 520 Series Cherryvile 120GB

Note: With all setting maxed in the game, running at a resolution of 1920x1200 I average anywhere from 16 to 22 frames per second. While I expect that number to increase with optimized drivers from Nvidia at a later date, it's stunningly low, even for an alpha test. I noted both GPUs at about 50% utilization walking around in-game, seems odd. Hope this info helps.

Reproduced by a friend. Moved from gunner seat to passenger seat, was seen standing on the seat through the vehicle roof.