Been leveling a Paladin since the Shattering hit, since I went Blood Elf Paladin, not a fan of Tauren Paladins, plus the name Glitterstorm goes fabulous with a Blood Elf(srsly, I killed a gnome priest while leveling, it was a 2-3 minute long battle because we could both heal, I ended up dancing on his corpse).
Had him at 20 before the Shattering hit and jumped right out there, it has to be the best leveling experience I've had in WoW, by far, I love how they revamped the HP of bosses in low level dungeons, as well as giving them toned down raid mechanics, requiring you use your interupts and utility skills wisely to ensure an easy success.
As well as adding quest NPCs at the start to compensate for the dungeon finder in a way that makes sense, the Undead are storming Scarlet Monastery and such, giving you orders on your way in.
I feel they did a fantastic job with Azeroth, WoW was already a cut above other MMOs, but this just sets the bar even further.