I don't know, I haven't even started, but I'm going to start. It's a very lightweight ruleset, bears some resemblance to Mongoose traveller in that there's a lot of 2d6 rolling (I think, I can't remember). Some things I don't like very much, like there's a distinct and obvious number of shots you can make before it becomes impossible to hit, which seems very artificial. Like, if you have a +1 to hit bonus, you can shoot like 5 or 6 times before the penalty makes it impossible to hit. It kinds of hurts immersion to have glaring game stuff like that.
Other than that it's awesome though. Huge amount of customization in the zombies. You can have fast, flimsy, 28 Days Later zombies, more traditional slow headshot only zombies, zombies that can use tools, zombies that can apply problem solving skills, all kinds of stuff. Humans can either be Norms, Survivors, or Inspired, which determines their skill and attribute points as well as whether or not they get special powers (No Inspired in my games. This isn't Dungeons and Douchebags, you can't be a wizard.) Last time I allowed one survivor in a group or Norms, to take on a leadership role, I'll probably do something similar.
Basically the game will involve surviving, scavenging, finding survivors, and eventually escaping. I am not afraid to kill PCs in a game like this. You will die.
Here is the old thread that I abandoned because I'm a horrible GM, and the first post has a detailed description of the rules, including a play example with Jim and Pam from The Office.