You have to hand it to Blizzard - they are pretty decent at telling an interesting story. Whether "being told a story" is what I'm looking for in an MMO in the long term remains open for debate, but in the short term I'm quite willing to take the bait and pursue a quest line simply to find out what happens next. In fact this is working so well that I've been zooming through both levels and zones at a remarkable speed for my standards.
The Eastern Plaguelands are still a lot more plagued than the Western ones, but progress is being made to heal them as well. Light's Hope Chapel is quite a quaint little place these days, all the watch towers have been turned into mini hubs, and I was most surprised to find that both the Infectis and the Pestilent Scar had been transformed into lakes. Even if there is still a lot more boring brown than I'd like, the overall mood of the zone has moved from depressing towards optimistic, just like in WPL, and I appreciated it. The Battle of Darrowshire chain still tugs at your heart strings (even if it has been condensed for convenience), but the main storyline guiding you through the zone is a more light-hearted matter that has you making friends with a lot of NPCs. Mostly I found them quite likeable, though the two paladins were very prone to repeating the same couple of phrases over and over in quick succession whenever they accompanied you out into the field, which got tedious somewhat quickly.
The zone also felt quite long. This wasn't a coincidence as I checked afterwards and the zone achievement contains a lot more quests than most of the other revamped old world areas. I don't want to say that it dragged on, because it never really felt that way, but at the same time slaughtering all those plague bats, undead and Scarlets certainly did bring back a bit of that vanilla WoW feel for me.
I was also pleasantly surprised when I got a Mr Grubbs. The pet collectors among you may laugh at me now, because you of course knew about this pet and made sure to get it the moment the Shattering hit. But I don't keep up with these things... in fact, I almost vendored the poor fellow at first because the icon reminded me of bear organs and similar vendor trash; good thing I noticed the green text. Once I had him out however and got to witness his wonderfully silly bouncing animation while idling in Ironforge, there was no end to my delight. I was most disappointed that I couldn't add the next three Mr Grubbses that I found to my collection as well, or at least pass them on to other characters. You take good care of these little guys, Mr Vendor guy, you hear me?
The only thing that I didn't like about the new Eastern Plaguelands - and I admit that this is a fairly minor complaint - was the fact that the last quest of the major storyline, no spoilers here, requires you to fight an evil mob alongside some NPC allies, but the moment you get ready to fight, the view switches to cut scene mode and you simply see the NPCs doing the job for you. You never even get to join in. I just didn't understand that. I may not be that fond of cut scenes to begin with, but I can see where they can serve a purpose to show something happening that isn't usually part of normal gameplay. But fighting a mob? That's the most basic unit of the game, why prevent me from joining in? Turning the act of playing my character into a passive affair of watching mobs die without any input from me is not a good thing.
Funnily enough, in the next zone I went to, the Badlands, Blizzard then immediately showed that at least some of their designers do understand that concept. The quest The Day Deathwing Came (and its follow-ups) has been praised by many and while I don't think it's that amazing (funny, yes) it's a case of clever use of game mechanics to make the player feel more involved instead of less. Usually when an NPC tells you a story, that either involves reading a lot of scrolling dialogue or clicking through several pages of quest text, but this quest has you acting out what's being told. There's another quest like this in Durotar, and it definitely makes the whole process a lot more fun and memorable.
On a more serious note, the Badlands were the first revamped zone I visited that didn't seem to be designed to progress you through roughly five levels. I guess after the Plaguelands the devs realised that they'd have to cram more and more quests into each zone in order to keep players busy for that long and just gave up on this model. The Badlands story only takes as long as it takes, which was two to three levels for me without heirlooms. It's a good story though, a little heart-wrenching in parts but with some very interesting lore implications. If it isn't continued in another zone, I hope that Blizzard picks it up again in some other form before the end of the expansion.
Oh, and one quest ended up being unintentionally hilarious: it has you fighting Nyxondra, a black dragon with a lot of whelps, alongside a couple of pet NPCs. I thought I'd be clever and pull her with my archer guy's ranged attack, but then it turned out that she also cast a fear every so often, scattering my little party all over the place and aggroing half a dozen whelps. Good thing that I was playing an invincible paladin, otherwise I might have been in trouble. Still, the whole thing felt a lot like a badly botched Onyxia attempt, which I thought was very funny.