It's entirely possible that this stuff is already up for more changes; I don't know.
My first impression of the water graphics: On my card, with my settings, the reflections don't work properly from most angles. Whatever is above the water on my screen reflects from the water, even if it wouldn't be above the water in the physical model.
Further, the water seems less 3D and more like a flat pane of smoky glass. It looks pretty awesome from above (reflections aside), but if you get too close it starts to look flat compared to the old water. From beneath the water, it just looks like a perfectly flat, dark ceiling.
My first impression of flying between old world zones: I'm not going to lie. Flying in the old world is awesome (especially up to things like the top of Blackrock Mountain or the Ironforge Airfield that I've been longing to get to for ages). However, there is often a very, very sudden split between old world zones graphically. The Northrend handles transitions by having them be slow and spread out, and/or by simply having each zone be similar and united in their snowy-ness. The Outland has slow transitions that seem to make physical sense (like going down a mountain path from Hellfire to the lower, wetter Zangamarsh).
Now compare that to the weird fissure that separates the big hot mountains of the Searing Gorge from the big cold mountains of Dun Morogh. That fissure reminds me more of the Outland in terms of "oh my the world is rent asunder and the terrain is changing like mad" than some of the Outland zone transitions do.
Now, I realize that Deathwing's escape did rend the world asunder to some extent, but there were no major changes in either the Gorge or Dun Morogh, so why are they acting like they're on separate tectonic plates?
Is this something that in any way affects the gameplay or my enjoyment of it? No, not really. In a perfect world, the transitions would be a bit less intense (except stuff like the Barrens where Deathwing really did rip it apart). But somehow, I'll survive...