Well, I'm enjoying the expansion.
In a relatively marathon period of play, I've gotten my main character (the Paladin) to 110. I've almost exclusively played on him, though I did just get Apocalypse for my Death Knight - I'm trying to decide whether to just get the artifacts on several of my characters now or wait until I'm actually intending to level them up.
The Broken Isles are pretty gorgeous - every zone is beautiful in its own way. I also greatly, greatly appreciate that there is a max-level zone - not a zone of pure daily quests (and in fact, daily quests are mostly replaced with World Quests - we'll see if they're better.)
The route I took my paladin through was partially determined by profession quests, so I went Stormheim, Azsuna, Val'sharah, and then Highmountain, and now I've started Suramar (though it looks like it's either going to be a huge number of quests there or that many of the chapters are going to be very short.)
Stormheim feels very much like Howling Fjord's sequel - it's a crag-filled area that heavily involves the Vrykul, but also ties things more directly to the Titans.
Highmountain is fantastic if you like Tauren. There's a lot about the history of the Highmountain Tauren as well as some very interesting tidbits about the Black Dragonflight (it was in Highmountain that Deathwing had his lair - including when he was Neltharion.)
Val'sharah is, in a way, the ultimate Druid zone. It's a beautiful forest very much in the "cultivated by druids" style, but the corruption of the Nightmare is spreading through it (and the aesthetic they've created for the Nightmare is super cool.)
Azsuna is somewhat less easily defined - I guess the main thing you'd focus on are ruins - the land here was shattered and the main focus of the zone is a kingdom of magically-bound ghosts and the Naga invading.
Finally, Suramar (a zone I have not yet completed, quest-wise) is a land utterly suffused with magic. There are vast subterranean structures outside the city, and then there's the city itself, which you'll approach less as an invading marauder and more like a spy infiltrating it. In fact, this might be the most Rogue-appropriate zone they've ever made.
The Legion certainly has a presence in each zone, but it's not all charred-black earth and green fire. There's a decent variety to the way that the Legion is working its mojo on each of these areas. They've wisely allowed the Legion to be a major presence without everything feeling the same at all times.
Now, regarding class quests:
I've hit a sort of speed bump in my class campaign - I need to send my champions on missions to pick up five quest items, with each quest taking about a day. Thankfully there are enough of these missions for me to send two squads at once, so tomorrow I'll hopefully be able to send out two more and finish it up.
There are definitely some enormous lore reveals happening in these campaign quests (the ones that all classes get, at least.)
Profession quests are... well, it's good that professions are getting some attention, but there are some speedbumps. For example, I need to make a thing in engineering that requires a Hearty Feast - something that I doubt anyone can cook up yet.
I've also done eight of the dungeons - all but the Suramar ones. It's incredibly late, though, so I'll just say that generally they're really good. I particularly liked Blackrook Hold, which totally gives you that "Dracula's Castle" vibe.
More specific updates will come later.