Game was pretty good, and exhausting (in a good way) - finished the campaign. Never had to mentally focus so much on an FPS before. I am in no rush to go through it again, especially on a higher diff. Think those special little Marauders f**ks will haunt me in my dreams for a little while. Once you figure them out it's not too bad, so long as you're not surrounded by other demons.
On to the multiplayer!