Bulletstorm is one of the best in the current crop of games. Although only in DirectX 9 mode, the rendering is pretty nice, based on version 3.5 of Unreal Engine.
All the graphics options were pushed to a max (high) and we measured performance with Fraps.
The Radeons do particularly well in this game, especially with antialiasing 8x. The quad CrossFire X gives no advantage over the tri CrossFire X system however.
With antialiasing 8x, the GeForces clearly lack memory with the surround set-up.