The Mists of Pandaria Postmortem: the Pandaren and the Wandering Isle.

With an expansion that centered around Pandaria and the Pandaren people, it would be pretty ridiculous to give them to one faction and not the other. Supposedly, in the initial design stages of Burning Crusade, the Alliance would have gotten the Pandaren instead of the Draenei. For whatever reason, that fell through (and as huge fan of the Draenei, I'm glad it did.)

One of the old design theories Blizzard had long held to was that of the "silhouette." One was supposed to be able to determine both the power level and faction of a character by their basic look. Transmogrification obviously changed that in terms of power level, but with WoW's first (and possibly only) neutral race, they completely abandoned this notion.

So, Pandaren actually get to level 12 or 13, completing all the quests on the Wandering Isle, before they are able to even pick a side.

The Wandering Isle is a fairly cool-looking zone, especially toward the end of its quests when you get to speak with the great turtle him(or her?)self. The Alliance and Horde do not play a major role in the quests there until very near the end, but you do get to see something of the two competing philosophies: Tushui and Huojin. At this point, they are merely different ways of looking at the world, but they will become the defining factors in one's future allegiance.

The Wandering Isle gives you a sneak preview at Pandaria, showing you Virmen, Hozen, and (as-yet-unidentified) Saurok. Likewise, you get to know the various elemental spirits as seen by the Pandaren, who seem a lot more affable than the ones you tend to encounter elsewhere in Azeroth.

With your decision made at the end of the chain, you have your meeting with either Garrosh or Varian, and from there your story is basically over.

While we might be seeing a little more of them in the Siege of Orgrimmar raid, for the most part the Pandaren of the Wandering Isle kind of fade into the background to make room for the mainland Pandaren (the exception being Chen Stormstout and his niece Lili.)

In terms of animation and model, the Pandaren are definitely recognizable as being far better-looking than the vanilla or BC races. While I can't quite tell if they're any fancier than the Cataclysm races, it's clear that the Worgen, Goblins and Pandaren all show why we need new character models for the older races.

Pandaren have a decent selection of classes, but the inevitable consequence of releasing an expansion with both a new race and a new class is that the vast majority of them will be Monks. This is even worse than in BC, when it seemed all Blood Elves were Paladins and all Draenei were Shamans. Over time, of course, this has become less of an issue, and I expect that one or two expansions from now, we'll see a large variety of non-Pandaren Monks and non-Monk Pandaren.

With this new precedent of a neutral race, it does open up Blizzard's options to introduce single races in future expansions. On the other hand, this could be a slippery slope into homogenizing the factions. While I think it made perfect sense for the Pandaren, I would hope and expect Blizzard to continue releasing races in pairs.