Context matters, and context changes over time, making the whole process more difficult. When Apple was exploring how to build the Lisa (their first GUI system)

Context matters, and context changes over time, making the whole process more difficult. When Apple was exploring how to build the Lisa (their first GUI system) they did user testing on both a single button mouse and a multi-button mouse. New users were confused by a multi-button mouse, so Apple went with a single button mouse. But as the years go by, and users get more sophisticated, it's clear that multi-button mice are better. There's no clear right choice that spans time. How fast are users going to come up to speed? What level of difficulty are you foisting on new users? Will they persist through that difficulty?