I found that I didn't really like anyone and killed someone every chance I got.
I killed the guy Playboy wanted me to killed, I can't remember his name. I killed the cop and you're damn right I killed Dimitri. I killed the person every time I had a choice to kill or not except I think I let the woman live who was cheating on the guy I killed for Playboy.
Ever since I finished the main storyline I haven't had any desire to play the game anymore.
I've never played online and I haven't done any side missions except the assassin ones. I get burnt out of the GTA series pretty fast every time even though I love the games.