To the OP, I have the Asus VG236H. I love it. I got it for around $300 a couple of months ago. It might not be the best as far as color reproduction comes, but it's a solid monitor for gaming.
So with a 120hz monitor do you run with Vsync on or off?
I did some research on this, and so many people suggested not using vsync with a 120Hz monitor. I found this to be pretty horrible advice, as the tearing was super noticeable for me with it off (above or below the refresh rate).
I personally always run vsync + triple buffering (D3DOverrider). I've never noticed a difference with input lag. I'm sure it's there, but it doesn't affect me. IMO, input lag is less of an issue than network lag, which I can pretty easily adapt to.
I got a 120Hz monitor because the picture is insanely smooth during movement. Turning off vsync completely defeated the purpose of having a 120Hz monitor, as the picture would now because noticeably less smooth looking because of tearing. For me, smoothness and no tearing greatly outweighed the benefit of lower input lag. I play better without tearing than I do with less lag that I can't even notice.