So I beat it on regular mode.
Then I went through and beat it on Classic mode(which was a bitch BTW) but I unlocked the Devil Horns. Those things are effing sweet. 1 or 2 shot kill on most necromorphs and the go down in like 3 hits.
There is some exploit where you can use the Devil Horns on Pure Survival mode, so I did that and went through that mode in about a day.
Now I'm ready to sell.
My review? If you liked the first two, you'll enjoy the 3rd. The game play didn't really change and the co-op mode simply adds to the single player campaign. It was nice to get some clarity on the plot too.