Scenarios are interesting. Hopefully a little more challenging than the Theramore scenario was, though.
Pet battles are amazing. I thought, "Oh, I'll just learn the skill on Aeven before I hit Pandaria and start gathering," and half an hour later, I had a couple of new pets and a fistful of new achievements. I can definitely see moar pet battles in my future.
The intro to Pandaria is a bit linear, but I understand that was to help introduce the idea of the Sha and the reasons for the Horde/Alliance interest in Pandaria. I'm OK with that, especially since it looks like from the second half of the Jade Forest on through the rest of the expansion there's a lot more freedom to accept or ignore quests. I'll be plowing through with Aeven until I can hit max gathering skills, but I plan on slowing down and seeing everything with Aetherna.
The Sha look like interesting foes. I'll need to be careful when I play through on Aeth and my other characters, though. Ive got Aeven specced as protection, which means she can gather up and wear down a large number of enemies at once. Some of the intro quests will be a bit trickier on a more squishy class.
Pandaria is obviously a land abundant in natural resources. I've not really even left the starting area (Pado'shan village?) yet, and I've already hit 550 mining/herbalism on Aeven, with 3+ stacks of ghost iron ore and 2+ stacks of green tea leaves. Note to self: next time, learn the new level of profession training before starting to gather.
The scenery is awesome.