X-bit Labs has published a review of the ATI Catalyst 9.1 drivers which were released on Thursday, you can check out their article over here. The reporter says the new driver significantly improves performance in both Quake Wars and Crysis Warhead:
The performance did improve significantly in two tests out of six we used in our today’s experiments - Crysis Warhead and Enemy Territory: Quake Wars. This gain sometimes reached 30-37%! It is a huge improvement for a new driver version. As a rule, in situations like that performance either doesn’t change at all or changes minimally so that you can hardly notice anything with a naked eye. I have to note that the performance increased stably only in Crysis Warhead, while in Enemy Territory: Quake Wars only dual-chip Radeon HD 4870 X2 benefitted from the new driver versions, which should have got correct multi-GPU support implemented for this game.