While the MP is as good or bad, depending on your perspective, as other COD games.
The SP is laughable at times.
I've only got as far as the first time you play as the dog and the game instantly killed me twice for not doing exactly as I was told. While you do expect a linear experience from COD, my experience so far is just plain stupid.
The first time the game killed me was near the start. My brother said follow and I didn't move instantly, so the game drop the roof on my head.
I'm not entirely sure why I died the second time. Me, my brother and the dog do a slow motion breach of a door. All enemies dispatched, so I walk through the door. Wrong! Apparently I did something to endanger the dog so the game killed me. After that I quit, I can't see me playing that through to the end.
I am enjoying the MP a bit more than MW3 though.