Highlighting Functionality
http://infocentre.frontend.com/infocentre/articles/highlightingfunctionality.html

Farrell, Tom
Frontend Infocentre
2006

Abstract:

Research indicates that most users never find the majority of the functionality in any given application. Learning tends to reach a plateau early on, and is rarely expanded upon. And what that means is that most customers consistently undervalue the software products they purchase and use.