As I write this, I've completed five of the nine missions that make up the single player campaign. Until mission 5, I have to say I was pretty unimpressed with the parts of the game you actually play (i.e. what you might call "the game"), but the arrival of a seriously enhanced flood and a bit more Cortana has made the game more interesting all of a sudden. The cut scenes in this game are long and cinematic, and actually detract from the experience somewhat because you just sit there for huge periods of time watching plot unfold. Clearly, these guys thought they were making a movie instead of an interactive experience.
Gameplay, sadly, is uninspiring. It's Halo, and there's nothing really new beyond some new equipment options (bubble shield, trip mine, etc.), which are admittedly nice. You can carry some big guns around, etc. I don't know.
I'm leaning toward doing what I did with BioShock sadly, which involved discussing an Emporer and various stages of undress. This game, like BioShock, has garnered all kinds of 10/10 perfect reviews. I have to wonder. Certainly, the single player game is not that good. And what's up with me finishing each mission in about 30 minutes? This is a short, short game. Unless you count the cut scenes, which are long. Odd.