When I play with extreme details on 1920x1080p resolution, I got 45-60fps, but I can clearly 'feel' when the framerate drops from 60fps to 45-55 on 60Hz.
An option for 50Hz would help keeping the smooth picture.
That's also a reason why Crysis 1 still looked very smooth without max. FPS for many people simply because it changes to 50Hz when you enable Vsync.