I just now tried the demo since the game was just released. 3 minute+ load times, preformance issues, buggy feeling weapon selection (as in I can't change weapons at all), and it even crashed on me once when I hit my right mouse button to see what it did. Though seeing that the demo was released back in Feb makes me more optimistic though, since that means they've had time to iron out bugs and such for retail.
Though I did get far enough to see enemies once, and they were nazi zombies, slowly lumbering at me. That alone would have made me keep trying to figure it out, but I wanted to sleep. Has anyone played the full game?
EDIT: I think I figured out the weapon selection and the cause of the crash. Despite tehre being settings for next weapon and previous weapons (which are set to mouse wheel up and down), pressing 1 cycles through left hand weapons and pressing 2 cycles right hand weapons. Attacking with your fist crashes the game. Well, the icon is an open hand, so maybe it's the game bitch slapping you?
And yea, the menus and stuff look ripped straight from Painkiller.