The more I think about this game the more I've soured on it as a $60 purchase.
A six hour campaign is perfectly fine in this day and age; ASSUMING there is some varied gameplay or epic set pieces. The Darkness 2 has neither. Granted I haven't finished the game yet (4 hours in), but so far I have seen everything the game offers within the first ten minutes. The actual gunplay is good, the guns are fun to shoot. But the firefights are completely bog standard corridor fare and the enemies are just boring. I've fought the same bad guys for 4 hours. Some guys have guns, other have bats. That's pretty much it. There is no big sandbox to play in like Halo, it really is CoD style level design but with worse shooting mechanics. The upgrade system is nice, but there's no upgrade that i'm on the jones to get, nothing that feels like it will help me in a meaningful way. As for the pick-up items and throw it mechanic, Bulletstorm did it much better because of the variety of items you can utilize.
The game's saving grace is its story; it's going in an interesting direction and it's DARK as hell. This game is very explicit, pulls no punches so for that, it's great. I don't know; if you enjoyed the demo, you'll like the game. Just don't expect to be blown away.