So much of what makes zombie survival mod DayZ so enjoyable to play is in the intangibles. You can't sum it up in bullet-points, or just say "it's fun", you need to experience a night in the dark with no food or water, on the run from both the living and the dead, to really get a handle on things.
Or you could watch this clip. Because for every epic 12-hour survival tale you'll have, you'll have another experience just like this one.
Day Z: IRL [YouTube]