"The Official Xbox Magazine (US) is amongst the latest of magazines to publish reviews on GTA IV. We didn't post all of them because it goes without saying that they'll all be fairly positive, and didn't provide much information of interest, unlike OXM. There are no spoilers within this article, except for the very last paragraph, which gives us the total amount of missions.
They gave the game a final score of 9.5/10, with the top two positive things being "wonderful environment with gazillions of great things to do", and "multiplayer is a deep, terrific addition to the series". A negative that they gave the game was: "Would be even better with a little editing: it starts slowly, has a few too many "filler" missions". That's interesting. I'm sure though it's nothing like Saints Row's concept of filling time up between its altogether 36 missions.
There are 11 main subdivisions that the city is split up in multiplayer, while it's been said that you can travel the entire city, this just means everyone will spawn closer together and ensuring the game doesn't take place accros the entire large map with a maximum of 16 players.
And speaking of players, just like Halo 3 and other select games, there will be a Party Mode. This essentially means you can invite your friends, create a party - and spend an entire evening of MP fun going from one match to another without loosing your favorite friends. If you like someone you found in a game, invite him to your party, that is if he didn't invite you!
Here comes that spoiler alert:
Thanks to Himuro for the news."
Source: Planet GTA