I want to give a Shout-Out to Terry Makedon, Catalyst Maker for his hard work in bringing drivers to ATI users over the last few years. His team is committed to releasing a driver every month or so and we've already seen 4 driver releases this year. Contrast that to NVIDIA releasing drivers every few months.
ATI's X1K series is the only one capable of HDR+MSAA at the same time. In order to enable it in a game like Oblivion you need to download "Chuck's patch". After setting AA on in the CCC control panel, you can enable HDR via the game's Options menu. Hopefully, we'll see more patches to enable this feature in games in the future.