Batman: Arkham City + SweetFX and FXAA
DSR 4x (1366x768 >>> 2732x1536)
Custom Resolution 4x (1366x768 >>> 2732x1536)
left = DSR, right = custom res
Hmm... they look about the same to me. Apart from some pixel differences due to the slight difference in angle between the two images, sharpness and clarity seem to be the exact same.
I remember DSR clearly looking blurrier than custom resolutions, even at 4x scaling. Maybe Nvidia changed it at some point so that "smoothness" at 0% actually disables the gaussian blur filter on top of DSR.
On a sidenote... Anything below 4x DSR still gives you improper scaling with a horrible image. How come they haven't fixed that yet? I can create a custom resolution to get 2.25x supersampling (1366x768 >>> 2049x1152, 1.5x on each axis) which is not nearly as demanding as 4x but still gives pretty good anti-aliasing and some extra clarity, but with DSR it's just broken.