580 gtx here too running game at 60fps in all zone and area hardly drop below 50. i say it stay at a solid 60 really but once in a while it drop to the 50ish for a sec then go back up. From my experience with messing around with the setting the General Drawing pack quite a perfermance hit once u go pass 8 and make ur video scream. I can always tell cuz i try turning AA on and off with the same setting except for the General Drawing. Fps alway drop 30-60ish whenever General Drawing is at 10 whether u have AA on or not. But i get solid 60fps whenever i put it at 8. I forgot what my fps is at 9 but at 8 my video card doesn't scream and run quiet so i decided on General Drawing 8. Basically u can have everything max on a 580GTX if u lower the General Drawing a bit. In my opinion i dont really see much of a difference between 8 and 10 anyways but that just me. Well i'm running in 580GTX SLi but i try turning one graphic card off and still have the same result. Also i don't think the game is fully stable for SLI or crossfire cuz the SLI bug me out on the movies. Doesn't bug me out in game but on the movies its flicker and studder hardly able ot watch. Also i use to play with a 4870x2. From my experience the game only use one of the 2 card on the 4870x2. If u disable one of the card on it u will have a better performance by disabling the AI catalyst. Sucks i know can't use both card but that the best i can help u on that right now unless they have fix that problem on a recent driver. I stop using that 4870x2 card now so i'm not in touch with ATI latest driver. Hope this help u guyz out a bit.
Resolution 1900x1200
Mutisampling: doesn't matter can put 16xq can still 60fps
General Drawing:8
Background Drawing: 5
Shadow: Highest
Ambient Occulsion: can be on or off same fps but i have it off cuz i don't like the game to be darker than it is
Depth of Field: On
Hardware mouse: on
Texture quality: high
Texture filtering: highest