I would assume this is what I have been experienceing lately.
My stats are in Sig, but to put it short, Phenom II 965 @ 4.0gHz, GTX 580 1.5gb 800/1600, 8g Ram, Win7 64b.
I run the game at 1920x1080, FXAA-Off, AA-Off, AF-Nvidia Forced 16x/off Ultra preset, shadows turned down to High, HDTextureDLCs.
Game runs at 60 FPS (Games Default VSync) outdoors and indoors, but it doesnt feel smooth sometimes, when i notice this, there is a slight fluctuation between 59&60 (measured with DXtory) usually when looking at objects in candlelight or at tables with objects and candles. Also corners with shadows. Perhaps its just more visible when looking at walls or stationary objects.
It's barely perceptible, but it seems like the game is stuttering alot more then 1 frame, but the fps doesnt drop lower.
Either way its there and it just kills me. I'm glad they have optimized what they have, its come a LOOONG way since release. I used to have to play with a FPS cap of 31 so i didnt notice the variations

If this is the same problem as mentioned above, i will try the fix. If it indeed works, my problems will be solved and i wont be in the forums much haha.