I've played the demo for about four hours so far. For the most part i'm really enjoying the game. I think they did a great job with the setting, really feels like you're in an old movie from the 50's. Cars are fun to drive, shooting is fun, overall a good game i think! I'll get it for sure.
By the way, in defense of Bose (not that i really want to defend him, but yeah)... regarding the comparison with GTA. It was funny when a friend of mine came over to check out the Mafia demo. We played the demo for about two hours, then we started up GTAIV just for fun. I didn't tell him about the argument in this thread, but guess what his first reaction/comment was... in his words: "GTA feels more lively, like, there's a much better atmosphere in GTA, everything is more smooth and fits together perfectly, blabla". And to be honest, i felt the same way.
GTA doesn't look as nice as Mafia II, but it's a lot more "smooth" and polished regarding feel and gameplay (IMO). No matter how much you've played it, the world and physics/gameplay (especially driving) feel just soo much better in GTA.
I'm not complaining tho, as i said, i really enjoyed the demo of Mafia II and i'm sure i'll enjoy the full game just as much. Just saying...