It has online multiplayer gameplay.. Like different online modes.. Deep character customization.. Ragdoll physics, and deep car customization.. More radio stations, and custom soundtracks.. Better aiming system.
But, I doubt it'll have more to do than GTA: SA.. For me, it's a holdover until the next GTA.. But, the fact that it's next-gen, looks great, and seems like it's going to play very smoothly, and different things makes it seem like it could end up actually challenging GTA, but I've been looking forward to this game since I first heard about it..