Me and my Halo 2 clan a few years back beat a group of surly airmen who used mouses and keyboards on their Xbox. Granted, they could turn faster then us, but it's nothing without proper communication and teamwork.
I don't have a problem with keyboard/mouse combo for consoles, I just choose to play the game as it's meant to be played-with a controller.
Ice, theirs a mouse/joystick combo for the PS3, think it's called the fragfest GX or something of that nature. Anywho, someone used it to get ranked #1 in CoD4, so apparently it's very well built.