ATI has released a patch for the ones engaged with Mass Effect 2 on ATI Crossfire graphic cards with anti-aliasing not available. This patch allow users with ATi Crossfire setups to use anti-aliasing, an option not available in the retail version of the game.
The download size of the patch is about 112 MB and you can download it by clicking here via FileFront.
Anti-aliasing is used to reduce stair-step patterns on the edges of polygons in games. It gives a smoother, slightly blurred look to the edges. Full scene anti-aliasing accomplishes this by rendering each frame at a larger resolution, then scaling it down to fit the actual screen resolution.