Graphically its very very good - the best game so far. Gameplay wise its just good. It no better than say Ghost Recon, but I've only seen the first 3 chapters so far.
One really annoying thing with it is the save games. I started a single player game and got to Chapter 3. Then went and played a co-op split screen with a mate and got to the end of chapter 1. Went back to the single player game and it wanted to start me from where the co-op game was saved. It doesnt appear to let you save different games, so no I'm not playing any more co-op until I've finished the single player game.
But yeah, in general its very good and probably worth the hype for the graphics alone, although COD3 is taking up more of my time.