I have it on Xbox 360 and it's one hell of a sexy game. It knocked Gears of War from it's top spot in my games list just after 15 minutes playing. Love the online too, can't get enough of them Search and Destroy modes.
It does have split screen, but not co-op. You can have 2-4 player split screen as a versus, though why you'd want to, I don't know.
On a side, related note; I'm working on a COD4 clan, if anyone is interested. Rank doesn't matter, just people who play often, know how to play and are generally well mannered, playing for fun. Send me a PM.