I've noticed in some of the videos that icons above enemy heads seem to be slightly more of a commonsight than in D2.
Now I don't want to upset all the wow-haters out there but do you think there will be something more extensive in the interface to help you keep track of buffs/debuffs on you, pcs, and monsters?
I think they should have at least some sort of textual or iconic indicator for your own buffs/debuffs (I believe I saw that already in the videos, ya?), but I would be fine if they chose not to go further than constant animations/auras for buffs/debuffs on others (friendly and hostile). Need to keep the action in action-rpg. Doesn't mean the game has to be "dumber", it just means you have to memorize more and do more work in your head and on the fly.
I'd actually prefer it if the debuffs on monsters stayed like they were in previous Diablo games, just changing them visually somehow. Perhaps exploding-heart-inflicted monsters can just pulse three times before exploding instead of the heart floater, etc. just like the elemental debuffs look.