Well, I have a benq xl2420t for 2 months now, and it is great and everything. Since this monitor, besides the 120Hz thing is also known has a stypid low input lag, I decided to try to compare it with the Wii U gamepad input lag.
I was expecting that this monitor would show the image slighly ahead of the gamepad, but to my surprise it was the exactly the same! I knew the gamepad was super fast, but I didn't though it was this much.
Here is the picture showing it:
My crap LCD TV also has the same input lag while in gaming mod, and it is much worse when not in gaming mode.
TV in gaming mode:
TV not in gaming mode:
This is not 100% related with the thread, but I think some people here might be interested in this comparison.
Edit: Ops, I'm using the direct images from dropbox. I'll upload them to somewhere else.
Edit 2: I fixed the images