Realisticly it's far better for a game to take longer to release than end up being a piece of turd like War Z, You have to also consider that the company, when they started day Z mod for arma 2 were just a bunch of guys whos mod exploded in popularity.
I am not defending the game or the developers, but actually, from their perspective it's smart to release the game in bits and bobs so it keeps players interested, if the game had been fully released instantly people would get bored, also it constantly lists its an alpha and prone to bugging, so I dont see how people can moan really, yes it sucks when i break my legs from a glitchy zombie and die, but i still enjoy the game, actually probably because im one of the 'bad community' for taking pleasure in killing