If you're a reflex god, which fortunately, I am. The game's animations are amazing; I especially loved the part in the building where you use the traps to kill the zombies. And the part where you drill the boss zombie's head while hanging on. Epic stuff man.
Though I think the game is fine the way it is, I can see how some people might think differently. The game is supposed to require quick reflexes and memorization. However, for the people who want a slightly less ... stressful experience, I do recommend a difficulty setting or something of that sort.
Overall, I think this is one of your best submissions yet, and I can't wait for part 3.