With Cataclysm I really loved the re-exploration of the old content, specifically the 1-60 areas. My guild and I all took off as soon as 4.0 dropped and went out to explore the world. From the new flora in Desolace to the water falls in Stranglethorn, it was very cool to see the world we had "grown up in" turned around and changed, in some cases, in such a drastic way.
There were a couple of areas that struck me particularly. Auberdine; the loss of Auberdine was very heartfelt. I took a worgen through the quests in Darkshore as well as my main and I truly felt the devastation of losing this portside town. The quests to find all the survivors mixed with the new music in the area can pull at your heartstrings.
Along the same vein the areas in Ashenvale where the Horde have encroached, coupled with changes to Stonetalon Mountains and the Northern and Southern Barrens made quite an impression on my Alliance tendencies.
The changes to the land and the changes to each factions land holdings is just awesome. It was quite a feat I would say, and it leaves me not surprised that the expansion lands of Cataclysm were not as awesome as they could be.
I enjoyed each of the new zones and found them quite expansive and enjoyable in story and for the general exploration factor however the problem is I didn't have to find them.
What I really disliked about Cataclysm in terms of exploration is twofold. One, that it was not really explorable. I had no "place" to go aside from a portal in my home faction city. Wow that takes thought. I enjoy the journey. With portals there is no journey. My exploration seemed to consist of figuring out the best way to port to my bank and get back to where I was in the zone so I could continue questing. I was so excited when I figured out I could fly to Vashj'ir instead of take a portal. Or that Hyjal was just a hop skip and a jump from Darnassus. I know, that seems crazy right? But really when you get ported in, you don't have to think about where the zone is located in relation to everything else...except the portal.Two; As far as the old content goes, I like the changes but I'm ready for it to go back now. I find I'm missing the old zones and the old quests. Not everywhere. But there are a small handful of zones that I find I'm missing the quests that used to be there. Or the NPC's that used to be there. Perhaps what I am looking for is resolution to some of the conflicts in those zones, I'm not sure. Either way it feels incomplete now. Change is hard for me I guess, and I don't like it one bit!
I think Cataclysm was mostly a success in regards to exploration . I just get nostalgic for the old ways now and again.