The first thing that struck me is the new face on Jaina. It looks... unpleasant. That's just me, though! It might just take some time to get used to it. Beyond that, the trailer is very very cool, and keeps the Alliance/Horde conflict in the forefront despite the departure from it for the raid zone. It reinforces my thoughts that Varian's hatred of the Horde is never going to be repaired until Garrosh is out of the picture. It also displays that the war on Ulduar isn't being supported by either the Horde or the Alliance: We're in this thing on our own. I also seem to hate Rhonin much less when Blizzard is writing his dialogue.
Thanks to everyone who wrote in about this!