MASS OF SCREENIES OF NEW ZONES - INSTANCES - AREA CHANGES. oh, note, MAJOR SPOILERS!!!
http://www.mmo-champion.com/news-2/cataclysm-zones-screenshots-npc-models/highlights for me. Mass increase in big Nelfie areas. some palces we love may have taken a beating, but look at Hyjal, Desolace, Felwood, Feralas.
Menethil Harbour is flooded.
Stormwind and Orgrimaar look epic - Note the destruction of the Park Area of Stormwind O_o (yes the main nelfie part of SW)
The goblin Cafe looking thing in Stranglethorn Vale
Thousand Needles flooded and no more raceway but a big floating barge in its place.
just go and see for yourselves.