… if we are competent user interface designers and can make our interfaces nearly optimal, personalizations can only make the interface worse. Therefore, we must be sparing and deliberate in offering user customizations. If a user can, by a few judicious choices, really improve the interface, we probably have done a poor job.
On the other hand, if a program’s interface is as dismal — to voice an opinion — as that of Microsoft Word 97/98, the situation is reversed. Almost any change the user makes is an improvement, to exaggerate only slightly. However, Word’s interface is not the kind of goal toward which we should be striving.
— Jef Raskin, The Humane Interface