I just finished the Pandaren starting zone with my new monk in Mists of Pandaria. I really liked the idea of questing in a zone which is located entirely on the back of a giant turtle and the rest of the lore in the zone was fun too. It was entirely on rails with no choice whatsoever for the character, which is bad, but the NPCs were really well done as they interacted with each other and had distinct personalities. If we accept that the starting zone is going to be entirely linear then I think Blizzard did a very good job making that linear story fun to play through. One thing that really surprised me was how difficult the zone was since I died twice and not due to some outrageous incompetence. There was one particular named mob that was extremely dangerous and one type of regular mob (the sprites that summon Mirror Images of themselves) that could kill me any time I pulled two of them at once. I am used to started zones being utterly trivial and this one wasn't.
Up until this point I have been very positive on the endgame of Mists but I have to register one really sticky complaint, and the forums show that I am not alone: Daily quests are far too necessary. I get Valour Points from doing dailies, dungeons, and raids, and the only possible way to spend them is to first do a crapton of dailies to unlock gear. I don't mind dailies being the gateway to gear but the fact that there isn't a single vendor I can currently use to spend my points is quite aggravating. Normally Blizzard does a pretty good job to separate the various parts of the game so you can progress without being 'forced' into any one thing but this seems like a real failure on that front. It isn't as if it would be difficult to address - if there was a single vendor who sold a variety of rings, or cloaks, or somesuch I would have no complaints. That would mean that I could spend a damn long time getting my rep up before I ended up with points I could not possibly use rather than feeling like I absolutely have to do a full complement of dailies every day to make use of my rapidly accumulating points.
I will give massive props on Challenge dungeons. We have been slugging away at them and I am frankly astounded at how hard they made the Gold level times. The first group to do them all did it by running without healers at all and using all kinds of tricks like invisibility potions and spec swaps mid dungeon and other aggressive moves and my group, despite being skilled, was laughably far away from the Gold times. We are going to try to rack up Silver times on every dungeon though and so far we are handily setting the pace for our server. Once we get all the server records sewn up we can start doing nutty things like cutting out healers and going full on consumables and such to try to get close to Gold times. These dungeons are well designed and really fun - not to mention brutally difficult, which I like. This is a fantastic feature for people like me who want hard stuff and aren't necessarily into a heavy raiding schedule so I give Challenge dungeons a big thumbs up. It may be the case that our current class makeup simply can't do Gold times at all for some dungeons but we will jump off that bridge when we get to it.