The touch display did more good for usability than any interface design or metaphor did the previous 20 by simply removing the layer of abstraction between the object on the screen and the user wanting to manipulate it. No more mentally translating hand-mouse coordination with eye-screen coordination.
I am not defending apple but I understand what they are trying to do which is to remove the need for metaphors by allowing you to manipulate the objects directly. I.e. the content is the metaphor for itself. Just like i don't need a metaphor for picking up a pencil i just do. Maybe they are not there yet but thats I price I think is worth paying.
Apple have far bigger problems than their interaction design IMO.