I have been playing almost exclusively AB the past 3 months or so and there have been alot of very competitive games. Id say that its pretty even between horde and ally as far as the wins go. Some days I will lose 10 of 12 and others I will win 10 of 12. I have personally been over 50% on horde but I know not by much. And its really nice how 24's dont make as much of a difference in AB as they do in WSG. Also, pops on horde side have been under 5 minutes, and if you queue right after a game it pops within 2 minutes.
Been enjoying myself there and its a shame most skilled people dont ever bother queuing AB.