Just started this morning. Playing on Deathwing. I've started an Orc Warlock, named Lurik, and an Undead Mage named Clisperson. Only 10 so far, and might end up re-rolling as an Undead Warlock.
I played retail WoW from vanilla up through Cata, and only brushed the surface of MoP. My main was an Undead Priest.
EDIT: Is there an XP multiplier on Deathwing? I can't seem to find that info anywhere, but it feels like I've been leveling really quickly.
EDIT2: Just saw in some other posts that the multiplier is, in fact, x7. So...question answered...