It doesn't work. Locked. Believe me i tried. I wanted to use r_displayinfo like the old games. Kinda disappointing. Don't know why they did that. Probably to prevent multiplayer cheating but they already are cheating somehow there.
I do wish i can use dev mode cuz i'd like to be able to see the ACTUAL game parameters and fps but there are other programs for that anyways.
Crysis 2 doesn't take much anyways. Crysis 1 does lol.