Yep, running everything at max, including AA, at 1280x960 but shadows disabled: smooth as silk.
Enable 1 notch on shadows: looks slow and jerky, control lag.
Seems like it's constanly rendering the whole sub interior as soon as you go down the hatch, instead of just rendering what is visible.
People asked for shadows, and they got 'm. But you need to turn them off for a playable experience.
* 8800GTS 512 btw