I just finished it. Really, this is a FUN game. Its asking a lot for 60 bucks tho. I'd say the perfect rental for this year so far. I got 835 achievements in a single playthrough on easy, loved the comedy, voice acting was AWESOME, and i felt the game played just fine. It wasn't anything extraordinary, but its a fun one-time through and i REALLY hope they make a sequel, some of the comedy in it is hillarious.
I'd give the game a B+, even on easy a few things were a lot more difficult then i imagined, but a good challenge and i never got frustrated.