I just started it. Only played a few hours and am only level 6. The game feels very nice (except for the movement/camera input lag) and is MUCH more challenging than WoW so far. I dont get many things yet, for example I seem to be leveling very slow, or be unable to kill mobs higher than 2 levels than me, or generally have not clue what some random sounds mean or other stuff that I get, but its still a lot of fun. I havent explored a lot at all. The game feels very new still.
Waiting for BIS to come back to their senses and do a real ArmA 2 successor.