On Buttons: Mobiles are the ultimate consumer computer. They are meant to be used by 12 year olds, teens, college kids, business people and your mother in law. But right now, the design of the interface is still way too confusing. Even Nokias which rank high on the usability scale have problems when it comes to using their phones. I was just talking to someone today about the “overloading” problem with Nokia. The re-use the same button for different, completely disparate tasks: like your power button to change audio profiles. What?! And the fact that if you click the menu button once, you go back to the home screen, and if you click it again you go to the menu, and if you hold it down, you get a list of running apps. On other phones, they have a tendency to do things like combine the power and hang up keys. Huh? The regular user wants One Button To Do One Thing.
On Form factor: I’d love a phone that was the size and shape of the XDA Mini II, with a QVGA screen and an OS that supports display in both portrait and landscape modes, but then it *needs* a slide-out data entry mechanism. In other words, what I’m thinking of is a keyboard that you can swap out. One keyboard you add slides one way and is a full QWERTY mini-keyboard (like a HipTop). The other slides the other way and is a normal phone keypad (like the Nokia 7650 or the new Samsungs). This to me would allow the user to choose their appropriate use case, but leave most of the phone alone for development. The QVGA screen would be big enough to play games and videos and maybe you could just go “free-form” with the phone and leave out the snap-on keypads/keyboards all together and navigate iPod style through your pre-loaded lists. Or I guess you could even use a pen (like the XDA works now), but I really think that’s going away completely. It just doesn’t work well.