PS. from http://developer.kde.org/documentation/design/ui/summary.html

Avoid cognitive excise (excise = tax). This is the cognitive effort the user must make to manipulate the interface, as opposed the effort spent thinking about the task.

One of the areas where software designers can inadvertently introduce significant amounts of excise is in support for first-time or casual users. It is easy to justify adding facilities to a program that will make it easy for newer users to learn how to use the program. Unfortunately, these facilities quickly become excise as the users become familiar with the program