I've just had a fool around behind the bike sheds with the Mafia 2 demo. It's definitely worth ten minutes of your time, and maybe another ten, and another.
You've got ten minutes to do whatever you like in a small section of the city. There's a mission to complete (which I didn't bother with), and a few streets of pristine suburbia to make your mark on.
Initially, I'm impressed with the cops. They arrest anyone who breaks a crime, they write you tickets for speeding, and their little hats bounce along the road when you send them tumbling over your hood.
I'm also impressed with the smashing into other cars and running people over. I have this game I like to play, "How long can you keep the mailbox sitting on your hood?"
Go grab it on Steam and find out.