I bought Arma II: Combined Operations during the Steam Summer Sale, and installed the "DayZ" mod a few days ago. The mod is incredible, to say the least. While the Sorce Mod: "No More Room In Hell" has a very intense and atmospheric George A. Romero zombie movie-feel to it, DayZ has a feel all it's own. I think the best comparison for "DayZ" would be "The Walking Dead".
Much like in "The Walking Dead", not all survivors are friendly. Some have become bandits, and in dire situations, your friends may turn against you to save themselves.
The desolate urban environment combined with flesh-eating zombies may seem generic, but since It's in the Arma II engine, it looks and feels real (to a certain extent). I was running down the street in the mod, bleeding, whilst being chased by a zombie that had gotten a taste of my flesh and wanted some more ALL OF IT!!! D: I had no weapons, and I was too scared to turn the game off. I just kept running. my vision distorting, my breathing quickening, my screaming gave way to sharp and painful wails. Eventually I stumbled and fell, and bled to death, while being consumed by the beast that was in pursuit.
The mod is difficult. Weapons are in buildings in towns, but that is also where the zombies dwell. Getting to a weapon is difficult, and even when you get one, ammo becomes your primary concern. I have heard that if you form a group, the game sheds it's difficult learning curve, and becomes a beautifull butterfly! really fun experience. :D
I have therefore started a Mod-Database group for those of you who would like to join together in-game to kill zombies, fix cars, explore, and have fun in the DayZ mod. Be sure to have a look, especially if you want to get ahead in "DayZ": Moddb.com Thanks for reading, and stay alive! >:D