Tried to like it.
I was one of the few whom purchased the game at the time it was still referred to as an "alpha". I understood that not all of the features listed on its website were going to be implemented in the game, but once the game was given a full release on Steam, these features were not yet released. Promised features not included were an XP system of leveling, player created missions, NPC guards around safe zones, multiple maps, 100 square mile map sizes, and many other features. None of them have been implemented as of the time of this writing.
Beyond missing features, there are a large number of bugs, some are fixed with each new patch, but still others are created. I've found my character locked in a room which was patched to seal up the building. My characters have also died as a result of running down a slightly steep hill. And, most maddeningly , I've been killed by invisible zombies.
Discounting the bugs and missing features, the biggest problem comes from the shoot on sight mentality of the game. While it was obviously intended for a lot of player killing to take place, it is taken to insane levels in War Z. Players camp in buildings or around the few towns to snipe players in search of food, often for no personal benefit other than the satisfaction of killing another player. This can make the raiding of towns for supplies an impossible task. The in-game deterrent for excessive PvP, the reputation system which will label a player killer as a "bandit" is completely ineffective as even if you see a player on screen, there is no way to tell if they are bandits or docile players until they begin shooting at you. This makes the War Z map a bloodbath of gamers bodies. Even the safe zones, which are supposed to be a haven from the PvP, just turn into choke points for player killers to snipe players hoping to stash their loot, making them the most dangerous parts of the game.
The reason for this excessive PvP is because, not only is there no deterrent, but there is nothing else to do. A typical "nice" session of War Z involves running across empty plains or forest, avoiding a few zombies, entering a town, finding a bag of chips and a bottle of water, and moving on. There is no endgame, no quest system, no reason to create community. This boredom of the players forced people to turn to killing each other to get what little enjoyment out of it that they could.
Now, on to the worst part. Even if you find a nice group of people to play with (a rarity) and they protect each other on their loot raids on zombie held towns, that doesn't mean that you are safe from hackers. Even if you spawn on a completely empty server to avoid other players, enough hackers exist to still ruin the experience for you. Hackers tend to jump from server to server and spawn on top of players, gunning them down from invisible locations, or simply causing their death by what looks like a brain aneurysm.
All in all, War Z was an ambitious, if somewhat derivative, game which has failed to live up to its lofty goals. It's only a shame that this game received so much media attention both before and after its release that it has become a top seller.