midnilux: I get 20-25 with ubersampling and SSAO on a GTX570, not worth it so I turned it off. I would rather have SSAO over ubersampling however, SSAO is a huge part of the game's ambience, you're robbing yourself of content by keeping that off. Ubersampling is pretty much just supersampling, you can enable that on any game through drivers, never been a big deal for me and the performance hit is too high.
Mhm...I think the world is much too organical for SSAO to be really noticed. Or do you inspect every single gras holm? ;) With all the normal shadows moving around, the vegetation and such...so I leave it off for some extra fps.
In more "urban" environments, like Dragon Age 2, it's much more noticeable; on the walls for instance.