I picked it up yesterday and spent about 10 hours playing. Overall it is pretty darn good. Not the best game ever, but very good. Think Grand Theft Auto in the Godfather world. Relativley few problems so far, and lots of fun stuff to do.
The bad: Frame rate issues here and there. AI can be goofy, but usually to your benefit (e.g. bad guys don't shoot) A couple of camera angles are weird and cause you to get stuck. They reuse building interiors too much so that all the hotels look the same, all bars look the same etc. This presumably cuts down on loading time.
The good: Playing the movie!!! You are the one who places the gun for Michael to kill Solotzo. You are the one who helps put the horse's head in Woltz's bed. You kill Paulie and leave the gun and don't forget the canoli! It's all there! Lightning fast transitions between maps almost no loading time! Loads of violence and blood. You get to toture and beat just about anyone like in GTA and The Punisher. The NYC in the game is huge and you get to roam freely and exort businesses when ever you want.
Over all it is a really cool game. It has a nice combo of linear and free form game play.