OK, well at least the cities feel bigger.
Org for instance - that'd always felt like a fairly small city to me and even putting aside the extra stuff added by Cata, when you simply fly over and just look at what's left of the old sections (and discover that even a 310 speed mount doesn't get you from one side to the other in just a few seconds) you get to truly appreciate just how big the place really is.
Or how's about Dire Maul? From the old perspective you really only saw what was in front of you and simply bee lined for whatever part of it you were going into, but being able to fly over the place one can't help but look at all of that real estate and appreciate the fact that it truly was a massive city at one point.
Now that everyone's finished the race to 85 I'd encourage all of you to start at the top of a continent and just grab a flight point to the southern half and actually spend the entire time looking at all of the awesome new changes and rearranging of the world as we knew it, as well as just doing some exploratory flying on your personal mount, not for the explorer achievement, but simply for the sake of seeing all of the new stuff as well as re-seeing the old stuff from an entirely new perspective.
Happy sight seeing!