Edward Tufte has posted a video that extols and criticises the iPhone UI design. He’s clearly a fan, and having played with the device I can understand why.
I thought his critique on the Stock widget was particularly interesting, though, calling the UI “cartoon like” and wishing that the data existed at “image resolution” rather then at the “resolution of Excel or PowerPoint”. You can understand this better with his comparison of the existing UI and how he would have done it (including a switch to landscape, higher information density and the use of SparkLines):
I liked the little comment he dropped in on the photo thumbnail view, that they should have used single pixel grey lines between the thumbnails, rather then the wider white ones. I’ve not looked at his books close enough to know why