Turns out the first hotfix (70517) ATI released for Far Cry 2 cheated, the optimizations sacrificed image quality for a bit more performance. Expreview tested both hotfixes on a Core 2 Duo QX9650 with Radeon HD 4870 and says the cheating driver, which has image quality issues, is about 10 percent faster.
The new hotfix scored 43.20FPS on their test system while the cheating driver gave 48.12FPS.