I’ve been playing FPS games since Wolfenstein 3D (and most people didn’t even use the mouse for those very early FPSes), and I have never considered trying that. As I said to a couple other people, I’ve accidentally set the X and Y to different values, and it just destroys my ability to aim.

But, ya know, I haven’t practiced it. It could offer an objective advantage, of some kind.

At any rate, I’m just glad there are people using it. It would be weird if it was a very common option in modern games, with nobody putting it to use, at all.