Personally, I really think the worgen took it on the chin this expansion. Not only is the female model lacking (in my opinion) compared to the original preview (that semi-permanent snarly and atrophied muzzle needs to be redesigned badly), but worgen players got to see their cool storyline concluded Horde-side while they were traipsing around in the night elf starting zones. Even today, most of Gilneas is a ghost zone. I love the worgen, and I really hope we get to see them get more involved in Mists.
As for winners, I'd definitely put Velen up there as a stealth winner. While the draenei still haven't been as active as I'd like, the quest in the Swamp of Sorrows where Velen appears is a huge lore goldmine for the future. Not only does Velen spell out the true nature of the conflict at hand, he sets the stage for a war so vast and terrible it makes all previous struggles on Azeroth pale to insignificance. He also flat out corrects the idea that the Light hates the broken, showing that it's the draenei themselves who have a touch of bigotry in their souls to conquer.
I could go on all day, but it's more interesting to see what you think. Winners and losers of this expansion? What are your choices?
World of Warcraft: Cataclysm has destroyed Azeroth as we know it; nothing is the same! In WoW Insider's Guide to Cataclysm, you can find out everything you need to know about WoW's third expansion, from leveling up a new goblin or worgen to breaking news and strategies on endgame play.