Check out this National Public Radio "Science Friday" interview with MIT professor John Maeda about ease of use and functional design. In it, Maeda and the host discuss several "laws of simplicity" (see also the book by the same name).
The first law is "reduce," which, paradoxically, might mean taking choices away in order to get to an object or technology's essence - a process of abstraction.
Naturally the iPhone briefly enters the dialog - an example of the seventh law, emotion. Diego Rodriguez at metacool aptly summarizes the physics of emotional design like this: "wanting something makes it easier to use."
Works for me.
Hat tip: Putting People First.