I spent like 4 hours today on the Trailer Park level trying to get Poetry in Motion. Like, seriously, I know the first 6-7 minutes of that map like the back of my hand now: what spawns in each round, where they spawn, where all the flares/flash-bangs/ammo locations are. I am perfect through the first 7 minutes and then it all goes to hell during a round with a splitter, a bird-man, and a grenadier. One of those three always gets me, or one of the quick bastards hits me right as I'm going to eliminate one of those. Dammit.
Also, I've gone back and played some of Alan Wake to pick up some achievements I never got the first time around, and man you can tell there's a huge difference in combat between this one and the original. American Nightmare is a lot, lot quicker. I think it's a good thing, to be honest.
EDIT: Another thing I've noticed is Alan took a trip to the gym between Alan Wake and American Nightmare. Wow the difference in sprinting is tremendous.