I experience the same exactly... I use fraps to measure the framerate, I get a solid vsynced 60fps in ALL quality settings. But even in low quality the movement is not fluid... stand still and turn and you don't get a fluid motion , it is like the game runs in a much lower framerate.
There are some parts that loading occurs and there is a small pause but I think those are normal.
I run the retail game on a E8500/3.16ghz C2D cpu with 8GB ram and a geforce285GTX that has 2GB of vram , all that on win7/x64 ...
