The Monk class is designed really well, though they are insanely OP in the lower levels, in all regards. My healer never loses mana and can stay alive with 3-4 guys on her, and this is without heirlooms!
PvP is a little iffy right now--there seem to be some serious balance issues at the different brackets (Priests, Pallies, Monks, Druid in lower brackets, Casters in upper brackets).
I haven't tried to the new dungeons or pet battling system yet (that will be my plan for this weekend) and I am seriously looking forward to it.
I love Pandaria! The world is awesome. I'm not terribly find of the Pandas (the females to me are bleh, the males are more tolerable) but the world is awesome, and the questing is fun and fresh.
Overall, I love launches. It's the only time I can tolerate server crashes and fighting for ores and mobs and being forced to just stand aorund watching all the chaos. It's part of the story of the launch and this one went pretty smoothly. I also feel like there is a ton to do in this expac and I am really enjoying taking my time to go through it all.