I run it on an ATI card, and what made the most difference in terms of my shots, and those from Lee and TJC, is HDR. Once I turned that one, I got the same effect in the pictures as they have, the "real" feel in them.
IF I edit the shots, I just put an overlay over it, in 10 - 20% visibility. It gives the color a bit more dept. Did that the first time on the F1 edition I posted here, but there it had a larger visibility. So, to see what it does, check those screenshots. 1 page back I think.
Further nothing is edited, just in game shots.