@Zwiebelchen: I agree as well. Flying mounts tend to ruin exploration. In MoP, Blizzard thought "oh it'd be okay as long as we prohibit them until you're 90". It helped a little, but at 90, everything became "fly here to complete this daily, fly there" without any contact with anything. It was a cool idea for outland (and implemented pretty well for Wrath), but I never wanted it for azeroth, and I definitely am glad they are delaying it in WoD.
On my first account (a trial account: gnome rogue), I traveled through duskwood, stranglethorn vale, wetlands, arathi highlands, ashenvale, and even a bit of burning steppes. I died incredibly often (trial account limit was 20, and many of those zones were much higher level), but it was such a cool experience exploring.
And I still remember trying to recruit for groups. It was a lengthy process of trying to whisper people around your level who could satisfy the roles. You were lucky if you could find a tank (usually it was just a feral in bear form or a warrior/pally with a shield) and luckier to find a dedicated healer (no dual-spec back then).
But those are mostly memories, and perhaps with a lot of silver lining.
I used to complain about all of Blizzard's changes and how they ruined the game's old "feel", but I've come to appreciate a lot of the changes they
did make. One of the biggest was cross-realm. I love it. A lot of people have mixed feelings about it, but it makes servers feel populated again. My two main servers lost a lot of population after each xpac, and it was like that for a lot of servers. I remember logging on to Cho'gall-US as alliance, and when I typed /who, there were only 2 alliance online (apart from me). And there was a guild called "The Resistance", which served to battle the population difference. Server merges fix the problem, but it also suffers fluctuations.
Cross realm, however, makes every server feel lively. You can see random people walking in lowbie zones, and you'll find more people to do things with. Also, you can easily play with random friends without having to transfer characters or level a new char (in case they play on a different server). It is great.
As for exploration, I enjoyed it a lot in TBC, Wrath, some of cata, and WoD (not much for MoP). In both TBC and Wrath, I was too poor to afford a flying mount, so I had to experience the world on foot anyway.
In cata, you should definitely try Vash'jir and Uldum! Vash'jir is by far one of my favorite zones. As for WoD, I love every part of it. There are some zones I prefer more than others, but it was the best questing experience I've had, and I did get some big "nostalgia" moments.
Garrisons + treasures = happy exploration. There are a bunch of treasures around draenor that you can pick up, and they are often in weird areas. Sometimes you'll have to climb houses or rocks, or you'll have to look really really closely to see them. Ultimately, I think Blizzard was a bit more creative with leveling and reducing tediousness in this expansion. A lot of people want that feeling they got when they first explored vanilla/BC. But blizzard can't achieve that with just new zones and new quests. Even if it is the same type of content, it won't necessarily give the same feel. But with the new additions in WoD, I've gotten quite a few of those "this is awesome" moments.
Oh, and make sure your music is on. WoW music has been consistently great. As for WoD, there are some callbacks to wc3 music, and that pleased my nostalgia glands.