Summary: Overall I'd have to give MoP 3/5. There are too many reasons to list in a small 3500 block of text, and quite frankly I don't feel like taking that level of time to explain. The one thing I will say that I don't like about it is that there are WAY too many time and money sinks in this expansion, and there aren't any real mechanics into balancing the player economy.
Summary: Well, I started playing World of Warcraft in the last couple patches of The Burning Crusade, so I know nothing of the Vanilla hey day (which actually in a lot of ways sounds like way to much work to me, all the stories my "in from launch" friends tell me), but I loved Wrath of the Lich King like I've loved few things (The Girlfriend, Family members and Employers I've ignored will attest to that I would probably have rated it third best gaming Experience ever, right after...
Summary: Bought this and played with my raiding guild but the game bogged down and got boring very fast. It usually takes a year or so before I get bored of a WoW expansion but this one only lasted a month. I can only hope that Blizzard announces something drastically new for the next expansion or an entirely new game as WoW no longer holds my interest.
Summary: After playing since beta, I did stop playing about 4 months after Mists of Pandaria was released. I don't know if this was merely 'growing up and out' of MMOs, or perhaps the fact that after that period of time, as a casual player, it became repetitive and unexciting. Now, I can really go far in repeating tasks over and over - I would rather level a new druid to 80 and delete it constantly... than play any more 'end game' MoP.
Summary: Certainly this is better than cataclysm, but if you came from Vanilla or Burning Crusade you probably are burned of doing the same thing, basically get to level 90, max professions, 2 weeks of heroics, then raid until another patch comes live, but with Pandaria they add something terrible you gotta do over 9000 daily quest... you'll be so burned that you don't even want to think leveling an alt and doing over 9000 dailies again.