My configuration: Mac machine using Win 7 with Bootcamp, ATI Radeon HD 6490m display adapter. And the game runs horribly, compared to what I see for consoles.
I tried different things, most notably installing catalyst control center and unchecking "Application Settings" for Anti-Aliasing and Anisotropic filtering in attempt to wake up the video card and boost the performance (was reading in some forums that the video card is running in idle speeds, that is why the frame drops).
No visible improvement of frame rate (especially Undead Burg, and other areas with fires, Blighttown is just awful).
Do you know any tricks?