Rather good.
The game as it is, is pretty good. It wasn't insanely impossible like other "Defend your base" type games. Plus, this also has an ENDING! ZOMG! =O
I do have a few complaints though...
1.) Accuracy: It was alright for the most part, just fix up the rifle a tad and make the shotgun have a bit more of a spread, and then make the sawed-off shotgun have more spread than the normal shotgun.
2.) As mentioned by someone before, the barracade should be customizable/upgradable. Maybe have some nice spikes on it to do a DoT (Damage over Time) kinda thing. Or just make it more durable.
3.) The variation between guns felt kinda weak... You basicly have a machine gun dominated invintory. I mean... Uzi or AK-47 + Shotgun = pwn. You won't lose unless you're an idiot. =/
4.) Finding the guns should have NO order WHAT SO EVER! It should be all random. That or you pick what weapon to go look for.
5.) Also as someone said before: You should be able to assign one weapon to one survivor. Or if you were to employ character types, have one type use a certain weapon.
6.) Employ hit-zones on the zombies. Two to five headshots with a handgun should put down a single zombie. Not +10.