I waited to really get into the gta4 experience before this...so I ended up finishing it instead. It really is fantastic
I got into the game bracing for some sense of unnecessary violence courtesy of my countrymen in scotland's rockstar office...but instead I discovered a matured incarnation of the series. 4 actually managed to grow up after a fashion.
The game is everything we remember and love, but takes it so much further, as though cribbing from the imagination of what gamer's hoped it could be. Crazy.
The story in the game is beyond compare, and -by itself- is the number one reason to buy this. It creates a journey, a life journey for Niko, and you'll be immediately drawn to see it through to the end.
Along the way, you'll occasionally remember "Holy crap! This is GTA! I need to go screw around!" And the multiplayer is totally there for you man! I thoroughly enjoyed all the modes; outside some of the street racing variants, that I think were done better in Crackdown.
All told, the critics have all been right. We likely are already looking at 2008's game of the year.