I'd have to agree with you on Duskwood. In fact, all the of the storyline in the human starting area I really enjoyed. It seems really cohesive, you're constantly learning new things about the Defias guys, and it seamlessly introduces you to the larger end-game stuff. Especially now that they've added more quests in Dustwallow linking the Defias to the Black Dragonflight stuff, it's all very cool.

In later zones, I think my favourite place is Nagrand. It's just beautiful: waterfalls, rolling grasslands, beautiful skies. I had high hopes for Shadowmoon Valley - the name evokes beautiful elven areas, and instead we got desolate, barren rock, with an almost industrial wasteland feel to it. I understand how it works with the story, but what a letdown

Winterspring; Snow and music.

Dustwallow Marsh is pretty damn awesome now. There are several zones like... Desolace that could use the treatment given Dustwallow.

The area around Brill is really cool, too.

Oddly enough, it's the same for me with snowy/wintry environments. I prefer Dun Morogh overall over Winterspring though; something about the lighting quality in Winterspring just doesn't quite do it for me. Dun Morogh is hands-down my favorite region in the game, and it was also my first experience with the game. What a hell of a one-two punch to draw me immediately into WoW and make me fall in love with it right off the bat!

Other regions I particularly loved:

Stranglethorn Vale - Scenery-wise, this is possibly the most immersive environment in the game to me after Dun Morogh. Just the way the undergrowth, jungle trees, seashore with coral reefs, and jungle hills all worked together made it incredibly impressive to me. Despite the PITA that traveling and questing was in this region, I loved it for the design and immersion.

Nagrand - Second most beautiful zone in the game. Between the landscape, with its rolling plains and mountains, the canyons crossing the middle, mid-air waterfalls, beautiful town designs, and well-crafted points of interest (especially the enigmatic massive crystalish mountain in the south), and topped off with a gorgeous sky, this is just a relaxing, gorgeous region.

I loved the primary human starting lands from an overall design standpoint and cohesive lore just like Rallick pointed out. Elwynn was the first mmo forest I played in that really felt right as a realistically populated forest between trees (especially tree cover overhead while venturing through), streams, and forest creatures all well-placed. The music selection and color palette for Westfall was perfect. Duskwood was also great, but I felt that the scenery wasn't quite interesting/varied enough. Too many wide open areas to genuinely get the spooky feel going enough. Redridge, while having a few interesting spots (love the town design) just never quite gelled with me though.

Thousand Needles deserves special mention for the awesome salt flats (for some reason, I love 'em), and the Barrens was the first massive-feeling region I ever played in an mmo after Asheron's Call's truly epic-feeling landscape. It also really felt right for the environment they were going for.

Arathi has been one of my favorite for a while. I like the smooth green hills and how the area looks as the sun goes down and at night time.

I also like the transition from the mainland of Desolace to its green coast.

I'll throw in another vote for Nagrand.

From the Horde side, the beauty of Nagrand combined with it's excellent questline (culminating with Thrall's visit) make it hard to beat. I really like the look of Zangermarsh, but the quests never gelled for me there. The spawning area in the southwest of that zone was an beautiful surprise. Feralas looked great as well, but no outstanding quest line I'm afraid.

For me, it's the zones with the lore I know and love. Tirisfal Glades, The Plaguelands, Burning Steppes, The Blasted Lands, and since the expansion came out, Ghostlands and Eversong Woods along with Silvermoon City.

In the old world I like Aszhara. The fall colors and the abandoned civilization just seem to integrate so well.

In Outlands, I think Nagrand is incredible. The floating islands and the rolling geography are just tons of fun. I also like Terrokar Forest. The Bone Wastes are cool but I never really appreciated them until I was running through a furrow in the ground. I realized that the furrow was carved by a giant piece of Auchindoun that was flung out from the explosion. That was the first time I really wished I could zoom out to a satellite view and see a given zone.

I can't stand the Barrens or Ashenvale. I'm not terribly partial to SMV either. Green lava is dumb. Ashenvale has a nice art scheme but poor level design. I've gotten stuck in so many roots that I hate going to that damn place now.

Lore-wise, the plaguelands were the zone I was most eager to adventure in, but then when I finally got there, the color palette really didn't work for me (can't quite put my finger on it, but it's never seemed right) except in the area immediately around Stratholme and a couple other spots. It just didn't quite gel with the areas as I recalled them appearing in Warcraft III.

It's hard for me to explain, but color and atmospherics make a big difference in my impression of an area. At least the plaguelands lore was awesome.

I've heard this from a lot of folks, but I think it worked very well. Plaguelands just looks dead. The grass is there, but lifeless. Not a single tree has leaves on it. The lakes are drying up, and there's nothing but undead in the zone. Not for everyone as you say, but I loved it

Seriously ? That was like, the loneliest place in the game. Could as well just play it offline.

Yup. Call me crazy but I really enjoyed that zone. I always play on PvP servers, so sometimes a lonely zone is a happy zone