Really good.
Look, I'm half way through this right now; And I'm absolutely loving it. It's great. It's unique I'm not sure how much I've seen this style of gameplay used before. And best of all it's fun. My only problem is... No boss fights. Would have loved some bigger or even just varied zombies. But still, really good game. Also, As I said, I'm only half way through, so if there is/are boss/es later on, I take back what I said and give you a 10. Love it.