Kind of slow
Has already been said, but it is kind of slow, made it to the end of the second map and just couldn't take the repetition anymore. Needs more types of zombies, different types of music, and needs to be more of a challenge.
Also, first time I purchased a barricade, I bought the wire one. About 6 levels later, I decided to get another wire one, and a little time later, i decided to get a wood one too. Well, apparently that overides the wire barricade and there is no way of undoing it so I was out 1200 points.