I'm curious also whether other users are running Crossfire.
With SuperSampling enabled the horizon and city object flickering is greatly reduced, however the drawback is that FPS take a hit.
Im running 1920x1200 all settings High, but mirrors off, shadows - planar, water normal, and 4xSSAA, 16AF. With vsync frames are avg ~30 in city areas and areas of high activity.
Before I take the plunge in a new card, I think I'll see how the i7 920 OC system performs with the single ATI 5870.