I only recently stumbled upon this whole thing and i'm seriously thinking of picking up the ArmA 2 combined ops bundle (i think that's the one that contains the base game and the operation arrowhead expansion) just to play it.
I've always wanted to get into ArmA proper, but after trying it a couple of times on other PCs it seemed that the AI is all snipers with perfect vision and the game mostly seemed geared to online play. Problem with that is i don't have the time to be in a proper multiplayer group and i don't have any friends who would be interested in some casual mil-sim action either, so i never got into ArmA until now.
However, i might be able to convince a couple of people to get into this mod and by extension, pull them into the basic ArmA gameplay as well.
It's always been one of the games i really wanted to learn how to play but never got around to. Maybe now's the chance