The questing in MoP is absolutely superb. The first MoP quest you start at 85 immediately shows you a cinematic, explaining the reason you are sent to Pandaria. I'm currently still leveling, but from what I've seen you can expect many of these cinematics that help progress the storyline. Questing, unlike in the previous 2 expansions, is more spread out across the zone. No more huge towns that give you 30+ quests, but smaller hubs with quests relating to that location. This feels a lot more natural and the quests are some of the most entertaining ones I've seen so far.
The new zones look gorgeous, the soundtrack is GLORIOUS and the voice acting has greatly improved. The new pet battle system is loads of fun and can keep you busy for hours.
I realise that these are but a few aspects of the game, and that a lot of people will rate it differently as they focus on other aspects like raiding and whatnot. But in my opinion this expansion is far superior to the previous 2 and definately does not deserve the "more of the same" comment that everyone seems to be giving it.