People don’t use a computer to enjoy the operating system; they don’t care about setting their system preferences, nor do they care about choosing what kind of scrollbars they want. They use a computer because they want to create something; they want to communicate with somebody; they want to express their own personality, everything from writing a novel to balancing their checkbook – some more fun than others, but it’s all about accomplishing something that really doesn’t have anything to do wtih using a computer. The computer is just a tool.
As interaction designers, we need to remember that it is not about the interface. It’s about what people want to do! To come up with great designs, you need to know who these people are and what they are really trying to accomplish.