after i beat this game i went through to try to find a few faults on this otherwise great game. i only found a few, and they are pretty minor all in all. first off, i think the handgun was a little over powered, i went through about 80% of the game with it, before i started going after the achievements. also i hated how during the tower defense on the invasion levels if they crossed the line, regardless of if they made it off the screen still counted against you. i never let one off the screen, but the damn dogs are too fast to stop at the lines on most occasions. besides those two things, everything else was great. the game is very easy to pick up and go, and the leveling system is damn near flawless. i wish i could have used the rage shots on the bosses, but it never seemed to work for me.
overall this is a very fun and gritty zombie shooter and i would definitely recommend it to anyone who asked.