Originally Posted by EMP
Yep, first thing I said as soon as I beat the game.
There honestly isn't much to do once you beat and 100% the game. It's a shame really, I put in countless hours after the missions in GTA3, Vice City & San Andreas.
As Slaytalllica was saying, I feel like an outsider in this game -- there's no core theme that holds everything together, nothing you could honestly relate to other than the music (assuming you're even into it.)
Hopefully the eventual DLC can help with this.