Although I had A LOT of problems with it, I can agree on Krzysiek. I had friends with same game, same OS, and roughly same setup, who had exactly none problems with the exact same disk.
Like I said, the problems were unexplainable, without errors codes or anything, just like it doesn't do anything at all.
Maybe we will find out about the future of GFWL when GTA V comes for PC, cause they need a solution for that multiplayer (which hopefully will be steam integration).