Very interesting!
I was always a fan of zombie stuff, but I think there have been few where I was actually a zombie myself! Granted, I still fight zombies but it's something unique. What made this great was that it was just so addictive. You pretty much did the same thing of fighting these zombies and slaying them over and over. Something can be repetitive and work if it's good. Besides, as you are the player you can put your own variants and styles in the game.
The music was also great and should be appreciated by all metal fans. The sound was really tough and it sounded authentic when your sword killed stuff. There were many aspects of it, yet it was easy to understand. I also liked how you had a good sense of using depth and could move around all places. The different locations and enemies helped too.