From a technical perspective, the servers have been completely stable, and I haven't encountered many bugs. A few interface glitches but that proved to be addons for me. I had one quest bug out and a relog fixed it.
The quest to get you going is pretty good. Not overly involved, and not high drama, but it sets the stage well. Things get going fairly quick once in Pandaria and thankfully it doesn't take too long to get something other than "Horde Smash" as quests.
There are varied types of quests, with some new mechanics so that's good, and the story is moving right along. There's a "make friends with the natives" plot that feels a little done before, but overall was OK. Also some genuinely funny moments as you go.
It's actually taken a little while to interact with more than just a few pandas which was a surprise, but it actually fits the story so I think it's working for me. Reserving judgement till I get a little further.
I just got to a point in the questing where I appear to have options and that has sort of opened the story up a bit. That can be tricky from a flowing story point of view so I'm curious to see how that works out.
Oh, and it's pretty. Really pretty. Didn't realize how much I missed that.