So we agreed on 3D gfx and more interactivity with NPCs. I also have another point which confuses me: Multiclassing in DD.
I think that MCing in DD adds a lot of fun. But it also allows you to overpower the game. So, I have a feeling that MCing should have its own downsides.
Maybe it should cost more skill points to get another class' skill or it could cost you Xp points. (Less XP from monsters.(Only monsters not quests!))
Something like that...