uhmm, it looks bad. Really, really, really bad...
You can unlock playing as Fettel... Who can pass through solid objects and is invisible to everyone, but Point Man, in cutscenes, but gets shot at constantly and can't penetrate widely spaced steel bars in actual gameplay.
Oh, and I wasn't kidding about stupid enemies - there are tons of zombies, infernal dogs with Doom 3 ash dissolving deaths and some other crap. Instead of advanced AI you'll be dealing with guys capable of infinitely respawning grunts. Hardest fights are not shootouts in FEAR 1 style, but brawls with enemies who teleport by walking through walls and carry deadly guns and heavy shielding. And you get locked with them in very tight quarters.
The most retarded episode was in the suburbs (COD MW 2 US suburb chapter was taking place next door). You get locked in a kids playground with some shed for cover and have to fight off a dozen soldiers and a power armor. The issue is... you're prevented from progressing until you're done by a wooden waist-high picket fence. With a wooden bolted gate. Which automatically opens after you've brought down the power armor, to let in the final bunch of soldiers. And no, you can't blast the fence with grenades.