I am personally ecstatic to experience the brand new flavor and style of the old world leveling zones. From what I've seen, Westfall and Tirisfal got a lot of love and I would love to see it personally. I've always loved the art in World of Warcraft, and the direction they've taken undead buildings in old Azeroth is nothing short of spectacular.
Also, Worgen. Werewolves are my favorite horror setting creatures, and now I can finally play one.
Also, new race/class combos. I'm an alt-aholic, and am already slavering to make a dwarf shaman or a Tauren paladin.
Also, the new talent tress. They look far more thought out, concise, and useful than ever before. And the idea of "feeling" like your spec early on is brilliant.
Also, Deathwing. I've got me some hardcore internet dragons to kill. And as everyone knows, WoW is about internet dragons.
Curiosity. New. Shiny. EXPLOSIONS. LAVA. GIANT HAMMERS. SMASHING THE CRAP OUT OF EVERYTHI--
ADD.
Excitement. The end. Thank you.