Well, im a tester I believe so I should give my input. So here goes:
1. Fix the REquires a Key doors, because some of the do not require a key, but an object or whatever.
2. Not as scary as you lead us to believe, so add in more things to create the atmosphere.
3. You need a story. Why are the zombies here? Why am I here? Maybe fill us in on that in the loading screen.
4. Add more zombies to the begining. Instead of a barrel falling down, make it a zombie.
5. The "look around cornors keys" (Q,E) are pretty much useless. Make E the use key, rather than enter.
Thats pretty much it, and i hope you learned some stuff by my suggestions. Good job so far.