Mostly I'm looking forward for lore of cataclysm zones. So far quests have been pretty much like "Go kill 10 boars because they killed my wife", and next the same guy sends you for quest that doesn't have anything to do with previous one (This started to get better in WotLK). From what I have heard, it'll be more like "Go do this and this" and after that the same guy gives quest which in you need to "Now that we have done [What we did in previous quest], you must do that, so we can finally do [next (end) part of the quest]" (Though with longer quest chains :) )
[The other things since only allowed to pic one :( ]:
I'd love to see for myself how the new DK rune system works, and how they have managed to turn blood into dedicated tanking tree and balance between DW and 2h Frost specs.
Also, as far as I know, new zones and old zone revamped, are looking amazing, and would love to explore them by myself.
Would love to see how they have managed to do all that phasing stuff in beta, since I have heard there are some quite amazing things.
Edited, Jul 29th 2010 7:45pm by Ugaskunkka