One of the amazing new features of the iPhone is it's revolutionary multi-touch display that lets you control everything by without buttons. You can glide through albums with Cover Flow, flip through photos and email them with a touch, or zoom in and out on a section of a web page. Check out this video of Jeff Han as he demonstrates how touch driven computer screens will change the way we work and play. By the way, the background tunes are pretty cool so turn up that volume!
Check out Jeff Han Multi-Touch Interaction Research for more info and videos.