As old time Unix and Linux user, I know my way around a system, especially using a shell. A lot of new users do not have this knowledge and it's quite eye-opening if you look over their shoulders and notice their problems and frustrations. Quite a lot of these are usability problems, everything works as designed but the user does not understand how to get it working.
It's easy to take users keyboard and do a one-time fix - and then the user is puzzled again next time the same situation occurs. Making the application do what the user wants in a way that the user can do it, is a real challenge and needs a good understanding of usability and of your users and their needs.
There are already some excellent books, like Alan Cooper's "The inmates are running the asylum", and for Open Source developers the openusability.org community.
I'm glad about Novell's usability studies that have today been made available under the Better Desktop Initiative. The material presented there might give some developers an eye-opener about problems that some users face today. I have been quite impressed during my visit to Cambridge in may to see the work done by the team for both GNOME and KDE desktops and hope it will have a great impact.
The press release went out a couple of minutes ago.
I'm looking forward to desktops that are usable for both geeks and "normal" users.