I'm really enjoying everything so far. Aside from the server hiccups the first couple days, which seem to have been fixed, I'm loving it. I'm in no hurry. I'm at 96.5 right now (lost significant time to server issues and RL over the weekend, but I don't care). Taking it as it comes. I don't want to rush and burn out and miss stuff.
The zones are simply amazing. They are head and shoulders above anything that came before. I have yet to come across an area where I just want to get out of as soon as I can (c.f., Desolace, Tanaris, Silithus, among others). There is detail and depth everywhere. It's great. I love the many little easter egg type things hidden around the world. The art is just fantastic. Stop and look at the trees sometime, for example. They're great.
The questing is really good. It's all still mostly variations on kill X, pick up X, talk to X, but they just seem more well done. There's definitely no shortage of quests to do, in my opinion. I was in SMV well past when I should have been because I was still following out quests.
The garrison is a really cool feature. I'm really enjoying all the activities it opens up. I'm a little concerned with the impacts it will have on professions vis a vis making money, but the garrison itself is really cool so far. I love the addition of the Lumber Mill. It's really cool to wander around and see trees that can be harvested. Makes the world that much more interactive. I hope they develop it more, like as another profession even.
I love the carry-over from Timeless Isle of the mob tagging. It's great not to have to fight to be the first to tag a rare or quest mobs. Bravo.
About the only downside--ymmv--is the difficulty level. There isn't really enough danger or fear of death, in my opinion. My first death in WoD occured at level 96, when I jumped off a ledge thinking I could use the slow-fall trinket thingy. Well, you can't instant cast it...oops...doesn't say that on the item! Guess I wasn't the first one, several guildies chimed in that they had done the same thing. Anyway, back to difficulty. The leveling dungeons are cake. I know they're just leveling dungeons, but they are really easy. I'm sure Blizz was trying to avoid a Cata repeat though. More than once, while exploring, I've run through some areas I shouldn't have that are filled with level 100 baddies, aggro'd a bunch, and made it out alive. Early on (Level 90-92 maybe), it seemed like it was probably just because I was decently geared (556 resto druid), but now that I'm more caught up with iLvl, difficulty still seems a little low. Really, though, it's not a big complaint. The positives far, far outweigh the negatives.
Oh, and I'm really enjoying the little touches that are obvious homages to Burning Crusades. Obviously we're in the same world, sort of, but it is also signficantly different from Outland. But, there are little things all around that just make me remember BC in a good way. It's very cool to make everything new, but incorporate the nostalgia, too.
Overall, at this early stage, I'm giving WoD a very hearty thumbs up! Really loving it.