I saw some of my friends playing this and bought the game in order to play this mod.
It's pretty darn good but definitely not for everybody. Simply because it is hard as hell, you spawn with no weapons on a huge map and you have to survive, find weapons, food, medical supplies, vehicules.
In addition to the zombies trying to kill you, most player are hostile as well and will shoot you on sight even if you are unarmed.
Plus the game is in Alpha, so there are quite a bit of bugs.
Here's a video for those who would like to know what it looks like.