Well...
I found this game to be quite fun and engaging. But, there were some things I didn't like about it.
Pros: I found slaughtering the hordes of zombies in each level/sub-level quite fun. It did get very repetitive at times, but that stopped when I got access to new weapons and the game introducing even more types of zombies. The game itself is pleasent to look at, and the animation is okay.
Cons: The music is VERY boring to listen to while you slaughter zombies. I mean, when you listen to the intro music you would think, "Oh man, the music for this game is stellar." But sadly, the music ingame is nothing like the intro music. I'd very much listen to some rock music rather than the ingame music. Another thing that bothers me about this game is the zombie A.I. Multiple times while I played through the game I found that zombies would try to run to me, only to get blocked off by a car, or another object. The zombies that did get stuck didn't try to get un-stuck, whick bothered me because it was pretty much a free kill. Thet last thing I have to say about this game is that the end bosses are ridiculously easy to kill. On the first boss I just had to run away from it as it charged me and I pretty much killed it. The same goes for the second boss, where I could strafe its ranged attacks and take it out with ease.
All in all, this game deserves a solid 8. I would like to see more from this user in terms of zombie games, so keep them coming.