As Jef Raskin put it, computer users are "stuck in this morass of overlapping windows." Looking at the history of the GUI from PARC to the present day, it's clear how right he was. Computers have used the same fundamental paradigm for the past thirty years. While this design serves well when you can only run a few applications, it doesn't really work with the number of applications that most people run today. Check your taskbar now, see how many programs you're running. Then think about how much time you spend shuffling between them and how much of that time you'd like to use for work.