Unless you really want to play badly and have extra cash, I wouldn't suggest buying ArmA: 2 and OA at this point if only for DayZ. If you want to play for Wasteland etc, go ahead. The standalone could be coming out any day now, and it will be better in almost every way. No more stuffty inventory system, bad car handling, terrible spawning system, useless zombies, and 99% of buildings will have loot and be enter-able.