Excellent post! I just wrote a silly little iPhone app in my free time, as a nice change of pace from my day job. One of the things I enjoyed most was the design process. These principles capture the things I worked hardest at. I did violate one or two of these since an equal purpose for me was specifically to learn iPhone programming, not just to be a creative expression. :-) The few listed here that I didn't spend time on give me something to think about for next time!