It's actually pretty hard to note anything unexpected or different in the Mafia 2 demo. Almost everything you'd expect from a game that borrows heavily from the GTA IV template is there, both the good and the bad.
The good is that the environment looks great. Players are transported to the mid-20th century heyday of mobsters, as seen in countless Hollywood movies. The voice-acting is spot on and the small amount of narrative we experienced is exactly what one would expect from a mafia saga.
The mission structure in the demo comes straight out of the GTA handbook: Protagonist receives a call, drives to where he's supposed to, a cutscene happens, the mission starts, another cutscene happens at some point, more action, and then the demo's mission ends. It's great ... once again, if you're looking to scratch that GTA itch in a new setting.
The combat in the game is solid. Think Gears of Mob and you're on the right path. Your character will shoot from behind cover, then slowly and safely move in to take out the onslaught of enemies. We had the opportunity to use a pistol, shotgun and machine gun -- all worked like you'd expect.
The only real criticism against this solid demo for Mafia 2 is how it lays out the route to objectives on the minimap. The artists and designers have spent so much time building this world; it's a shame that, when driving, your focus is taken off the detailed environment. It basically turns driving into the minimap following minigame. It's a problem that many other sandbox titles have solved by putting subtle (or blatant) directions on the main screen for the player to follow.
As for Mafia 2 3D on PC, if you've got a couple thousand dollars burning a hole in your pocket for all the required equipment (superpowered PC, glasses and TV) -- do it. It definitely looks great, but the cost of entry seems a bit steep.
Mafia 2 is shaping up to be exactly what we'd expect, and we're not about to complain.