ATI being able to do HDR and AA at the same time is nice, I didnt know it did that because on my computer, see sig, I cant enable both so I figured it was a game feature, not a gfx card specific feature.
After spending hours with tweaking Oblivion settings, I have figured out one very important thing, turn off the grass, completely. It only adds visual candy and does nothing for the gameplay, it also MURDERS FPS. With grass on the default setting, my FPS gets cut in half. I dont have HDR or Bloom, or even AA on just cause I prefer to run at a higher res then have those 3 options on, I figure why have AA on if I can make the res bigger? it accomplishes near the same thing. I run at 1680x1050 (widescreen mind you) with just about every setting, but Shadow smoothing and Grass, on to max or near to it.