I felt the need to write about Vashj'ir and Uldum after I first quested through them, but not about Mount Hyjal, Deepholm and Twilight Highlands for some reason. There was nothing terribly wrong with them, but there also wasn't anything that left enough of an impression on me to make me want to write about these zones while I was still distracted by the levelling experience as a whole. Now that I'm going through the those same zones again on my alts however, I'm trying to formulate a bit more of an opinion on their questing.
I have to admit, my first impression of Deepholm was largely one of "ew". Some people have compared it to Outland, what with the floating rocks and all, but even though I love Outland in general, I was never particularly fond of the really darkly coloured zones there (Netherstorm and Shadowmoon Valley) either. Deepholm is worse because it doesn't even have Outland's beautiful skies. In fact, it has no sky because it's effectively a huge cave. I hate caves in WoW.
With that in mind, I wasn't exactly predisposed to like the zone. In fact, my dislike incrased when I realised while levelling my first alt that Deepholm was a bit of a bottleneck in terms of questing. At eighty, you can choose between going to Mount Hyjal or Vashj'ir, and around eighty-four you can choose between Uldum and Twilight Highlands. But around eighty-two or so, when you've completed the first Cataclysm starter zone of your choice, your options feel kind of limited. Yes, you could do the other starter zone, but the mobs will feel weak and the quest rewards likely won't get you any upgrades. At the same time going to Deepholm and unlocking Therazane for the shoulder enchants (which are not BoA yet) is a bit of a must. A choice that is so obviously biased towards one option is not much of a choice.
However, once I overcame those reservations and actually played through Deepholm a second time, I was pleasantly surprised. It doesn't apply many of the "revolutionary" new techniques that bugged me in other zones, such as cut scenes or forcing the player through a wonky storyline. The phasing is comparatively subtle, you spend a lot of time flying around and killing things the old-fashioned way, and the whole thing about having to repair the rift between the planes actually feels like a serious threat (as opposed to being ship-wrecked or captured by pygmies). Also, while the progression through the zone is still very linear, it doesn't feel quite as bad as in other zones, simply because it's not underlined by the geography. Or in other words, you get sent all over the place instead of slowly meandering from mini hub to mini hub, never to return to where you were before. I never thought that I'd long for the experience of quests making me run around, but there you go.
Other things that the zone has going for it are the fact that Therazane is one hell of a woman, her daily quest hub is quite solid if you like doing daily quests (like I do) and, of course, Pebble. Who'd have thought that you could create such a thing as a cute rock?
I did have a couple of quests bug out on me in annoying ways during my first playthrough, but the second time around things mostly went smoothly. Except for Quicksilver Submersion. A quest that forces you to hide in a very specific but not specified spot barely out of aggro range of some killer elites just to overhear a conversation is just poor design.