Very well done, the zombies really put the pressure on and you need to learn how to prioritise and manage your weapons properly to stay alive. I was a little frustrated at not finding a single survivor until the second area (is that normal?) but them's the breaks, I guess.
Just a few things about the combat:
a) Why does switching weapons take as long (if not longer) than reloading? Seems like it should be something you can do really quickly. Also, if you only have access to 2 weapons having one button that switches between them makes more sense than a button for each.
b) I'd like something that shows me which firing mode I'm in please, rather than wasting a bullet to find out or having to remember. What do you think about taking away the barrier health indicator? Maybe replace it with messages popping up every 10% or so telling you the barrier is in trouble. It just seems kind of silly that we have a psychic connection to the barricade that tells us how strong it is but we don't know the position of one little switch on the gun in our hands.
The Last Stand is an awesome game, and this seems like that but with a different view in combat, and with the difficulty ramped up to 11. So still awesome =D