I was a sophmore in high school when I first played Grand Theft Auto 3. Immediately, I knew that this game needed so very badly to become an MMORPG. While it isn't exactly GTA the MMO, All Points Bulletin takes everything you could want in a gritty cops-and-robbers game and delivers it up on a massive scale. I spent a solid half-hour at PAX East 2010, trying out this promising new title.
Carjacking is a lot more gentle in APB than it is in the GTA games, with no roadside beatings in evidence. It works on the same basic principle though, and APB will have more than enough carnage to satisfy the most bloodthirsty gamer. Cars ram and react to damage well, although without nearly as much detail as you see in GTA.
Combat is a lot of fun, and the gunfighting in APB is much better than anything in the GTA series. Red Dead Redemption ensured it wasn't the title at PAX with the best fighting, but APB was a not-too-distant second. Knocking enemy players unconscious keeps them out of the fight for twice as long as killing them, and an arrest stops a player from being able to act for up to 30 seconds.
As much as I enjoy being an anarcho-punk gangster, there's something seriously satisfying about locking other players down for half a minute at a time. APB uses directional voice chat, which means you can hear the people who are physically close to your avatar talking. Arrest someone, and you'll have the fun of listening to him scream for his friends to help.
I'm not sure if APB will ever have what it takes to be a success on the scale of the GTA series, but I'd be surprised if it didn't attract (at the very least) a sizeable niche following. This game delivers brutal, fast-paced cops and robbers action in a persistent world. What more could anyone want?