Made available by ATI just a short while ago is a beta "hotfix" Doom3 boosted CATALYST performance driver as mentioned by Hexus in a recent posting. The intrium driver (leading up to the 5.11 officials) is said to boost performance by up to 35% with AA enabled in Doom3.
Pity it wasnt around back when the game was initially released, as its common knowledge NVIDIA did far better in the performance stakes with this particular blockbuster title. The good news is that this would suggest theres a nice OpenGL speed increase across the board. To see if this is the case, why not try them out for yourself?