Some day this year I’ll be able to comment on this more. (The iPhone is not out in Switzerland yet and I am waiting for version 2 before I buy one, yadda, yadda, etc.)
For now, here’s an interesting discussion about the iPhone user experience and the way its apps display information:
graphpaper.com - Edward Tufte’s iPhone
It will be interesting to see what kind of user experience third party apps will offer when the official SDK is released.