some nice articles to read, I think they'll make things clear :
ussability guru Jakob Nielsen :
http://www.useit.com/alertbox/20001029.html
idea Generator vs Jakub Nielsen :
http://www.flashthief.com/hotarticle...husability.htm
I forgot to mention: Nielsen's company works for Macromedia now
http://www.ddj.com/news/fullstory.cgi?id=5957