iPhones and buttons in the user experience
The iPhone user experience is all about not just touch but multiple touch. When designing user experiences for the iDevices, try not to use buttons.
There are many gestures that a designer can use to replace buttons and thereby make the experience of using the iphone more realistic and interesting.
I am a big fan of the swipe gesture. The use of the swipe gesture for navigation is one that can replace the button in many cases. A swipe can take you to different parts of the application without the use of the button.
There can be uses of the swipe gesture in scenarios like the log in screen where one might think replacing the button might be too hard. Why not just swipe to login? It just makes lifer a little bit more interesting.
Then you have the multiple touch gestures like pinch and multi finger swipes, amongst others. These gestures can be used in innovative ways to provide a sense of realism and even awe. A pinch can be used to, say delete a data entity (think deleting a message in email). A multi finger vertical swipe might lead to opening up a detail view of a data set.
More innovative uses of the whole touch and multi touch gestures can be thought of. Give it a serious thought the next time you are designing an iApp. Your users might get positively surprised.