I loved this summary of the iPhone GUI, by Edward Tufte

"The design ideas here include high-resolution touch-screens; minimizing computer admin debris; spatial distribution of information rather than temporal stacking; complete integration of text, images, and live video; a flat non-hierarchical interface; and replacing spacious icons with tight words. The metaphor for the interface is the information. Thus the iPhone got it mostly right."

Read the article, and watch the video too (it's cool).