The Interface is the Program, and it ain't Agile: "I've seen a lot of Agile projects crash and burn after about their third external iteration for lack of good architectural foundations. It doesn't take much architecture to shape the whole -- just enough to keep Conway's Law happy and to lay a foundation for the interface -- but it takes much more than Ron Jeffrie's fabled "ten minutes of design." Maybe a sprint's worth is enough to get started.
If an interface is unproductive or inhumane, users notice it only after a long enough time has elapsed for habit formation to be a factor. You don't notice such things when you test drive the program; the clumsiness is hidden behind the familiar Redmond look-and-feel or behind some graphic artist's sugar coating. "