I know this is an old thread, but I got my BenQ 120hz monitor delivered yesterday. Installed the monitor using the Dual DVI cable, set nvidia control panel to output 120hz and then the fluid motion began.. even basic silly stuff like window dragging was more fluid. I went online and found some user configs for the monitor, got my colors, brightness and contrast set, saved the profile and launched up BF3.
Sorry to tell you naysayers but you are flat out WRONG, there is easily a difference between 60hz and 120hz gaming, Maybe it's just my 20/15 vision (no contacts or glasses) or maybe you have a junk video card (mine is GTX 670) but the difference is very clear, to use the words slight or moderate doesn't fit the difference I see.