Design by Iteration
A few months ago I mentioned the design of ConvertBot, a unit converter App for the iPhone. The first impression of the design was great, but using it became a pain. Lots of units are missing and I never really got used to the circled main widget for choosing units.
Today I found a blog entry “Convert design evolution” of the making of a new Converter App (iTunes Link) by TapTapTap. No question, you now have the second (and much more important) ingredient for great design: iteration.

