I played on hard mode, which, now that I know how easy unlimited ammo is to unlock, was a mistake. I died alot, mostly when I was still getting used to the controls, and again when fighting the elevator boss. The bot would drive me nuts sometimes, especially when fighting the two chainsaw guys in the oil rig - If you go down the zip line ahead of her, she'll just stand there and get decapitated until the zip line comes back. It was infuriating and I only got by it by getting a real person to play her for a bit. Also, whenever I ran away from something and did a spin and readied my gun, her head would ALWAYS be right in the way. She'd take 1-2 seconds to move, but when a reaper's coming at me in it's one-hit kill stance and I can't shoot through her, it had me yelling "MOVE!" at my screen a couple of times.
I like the co-op idea, but people who had to play by themselves, like me, were probably needlessly frustrated. Not to mention that the survival horror is even less prevalent in this one than in 4, though that's a matter of taste, I guess. At least in 4, Saddler's 'right hand' was scary. Then, of course, there's the ending.
I know alot of people don't care about the story, but I do (did). Other than that, the game was fun and awesome and definitely purdy, but after beating it once, I've put it away for a year, which is a lot less than I was hoping for from this game.