I think the biggest change and most wanted "feature" is a smoother UI, (which is what really makes Android UI not as pleasant to work with as ios), and now that we got it with Butter, I'm wondering for those that know the actual programming guts, is it a true fix in the way Android handles the UI or is it a complicated added "fix" that is a workaround for the problem. I remember reading a while back that the way Android handles the UI was fundamentally flawed and the whole code would need to be rewritten to fix it which Google was not willing to do.