[37signals] There's an interesting tradeoff presented by the iPhone. While the phone can do more, and its interface is fluid, in some ways it widens the gulf between human and computer.
When you touch it it doesn't touch you back.
That may prove to be a good thing. It may prove that what we think we need we don't really need. The tradeoffs may payoff. But we've certainly lost the tactile feedback humans are used to when dealing with things that are right in front of us. Now the connection is simulated. Rich textures have been replaced with androgynous glass.

How can you dial the iPhone without looking at it? How can you reach in your pocket and press "1" for voicemail? How can you orient yourself with the interface without seeing it? With a traditional phone or device with buttons you can feel your way around it. You can find the bumps, the humps, the cut lines, the shapes, the sizes. You can find your way around in the dark. Not with the iPhone.