In The Command Line—The Best Newbie Interface?, Richard Wareham makes a case for a command-line user-interface being better—even for non-technical users—than graphical user-interfaces. A case based on his experience teaching a beginners’ computing course.
It’s an interesting line of thinking. If a fraction of the effort that has gone into GUI’s were applied to command-line interfaces (not—by the way—to discount the advances that have been made), I think his case could be bolstered considerably.
I probably spend roughly equal time with both types of interface. Which suggests that—for me—each has strengths & weaknesses; neither being superior. I have a tendency, however, to think that this balance wouldn’t hold for average users.