There are many lessons to be learned from this add-rule task. After the original task's GOMS/heuristic analysis and two redesigns, each with their own analysis, one lesson stands out above all the others as the main lesson to be taken from this paper: Interface Usability is a finicky business. It is made even more difficult if there is no clear target audience in mind. When the target audience is made too broad, as is the case with many Microsoft products, and too many accommodations and features are added, product usability is weakened.
Surely, creating different designs for different people should not be the solution. A more reasonable answer would be to start any design process by clearly defining the target audience. As has been shown in the case of MS Outlook Express rule creation, interface design becomes fantastically more difficult when designing for a broad, general populace. restart>>