i own the game, and i bought it through steam, along with having to run the steam client to play it, i also have to run a rockstar cleint... and then once the game is running if i want to auto save i need windows live running. Along with this my PC struggles to play this game even with 3 GB ram, 512 MB Nvidia gfx card (9600) and 2.6GHz dual core proccessor.
The game somtimes runs at a really low frame rate (almost unplayable) and also sometimes the textures dont load, either partially or at all. Also the online multiplayer isnt too amazing as there arent many people on it (max i have played with is about 4-5).
But if you can get past all of that crap it is pretty fun to play...