I just finished it last night and I have to say this is (personally) one of the best games I have played.
Not because it does that much new but the voice acting, the music (omg the music), the characters and the relationship you build with them are all tremendous. This is hands down the best open world and Rockstar game for me.
I feel that companies like Rockstar and Bungie (specifically ODST) are taking huge steps to making the stories in their games much better. Developers need to stop just doing the action movie game. They underestimate the power of an amazing soundtrack and thoughtful story. If games continue like this then we all benefit.