A 225 km2 open world post-soviet state wiped out by an unknown infection. Go Solo, team up with friends or take on the world as you choose your path in this brutal and chilling landscape using whatever means you stumble upon to survive.
Bought ARMA 2 for this, was sadly disappointed. Possibly the most over-hyped mod of all time, in my opinion. It claims to be a "realistic" survival experience, but of the four times I died, I had to ask myself how "realistic" those deaths were. Most were from jackasses with sniper rifles who shot me for no reason, the others were from zombies with teleporting and/or invisibility powers. Great idea, horrible execution and player base. Sniping an unarmed guy you've never met isn't "paranoid" it's being a troll.
Very steep learning curve and very challenging gameplay may turn off newer players, but the mod has it's moments. However, if you're a beginner, you'll usually find yourself wandering aimlessly for hours until either a zombie kills you (you start with no firearms, no weapons, barely any supplies), a survivor or some script kiddie who decided you would be his or her next victim.
The mod also features plenty of bugs, though this is expected as Arma 2:CO was very buggy to begin with. Though it has a fairly nice-looking interface and the level of realism is certainly high.
You'll have moments where you like this mod, like if you play with a friend, though it's likely newer players will be turned off by it's long list of problems.
This is really just my opinion of course considering how big this mod's fan-base is, I don't expect a lot of other people to agree with it.