Yes, mouse/keyboard offers more precise controls. But it doesn't mean jack shit unless you are competing with two different inputs. Sure, if someone with a controller was competing against a person with mouse/keyboard, they would very likely lose. But there has only been like 1 game where console players and pc players could compete. I happen to be able to maneuver and play games on either a console controller or mouse/keyboard very efficiently. I really could care less what input I use as long as the game is fun and the people I play multiplayer with are enjoyable to play with. I grew up playing Quake, Tribes, Doom, Rise of the Triad, etc. I will play any FPS you throw at me regardless of the control scheme.
And Halo felt wierd on PC because of the momentum and weight that Bungie(and Gearbox didn't adjust I guess) developed for the games' dual analog console controls. It just didn't move around like normal pc fps' camera/character on a stick.
Essay Pro