The Darkness II's project director, Sheldon Carter, hinted around a bit about the storyline in the game to Destructoid during GDC this week.
While he wouldn't go into too much detail on it, Carter did talk a bit about Jackie's powers and the additional ways he can harness the Darkness this time around.
One of the new ways, is the demons arms can work cooperatively. The left will grab an enemy while the right one dispatches it. Since the left one is the official "grabber", you can use it to grab objects and toss them at enemies - even impale them.
Go watch the interview here or below.
The Darkness II is out this fall on PC, Xbox 360, and PS3.