I just had to post something to comment on the Mac OS X Leopard Time Machine user interface. I mostly use Windows, or Linux some times, but a coworker has a Mac laptop on which I was able to see the Time Machine program running. My first reaction was “Wow” and the reason being is that I believe it is a great user interface. Its spatial organization of the windows overlapping matches our mental conception of things going “back in time.” It isn’t cluttered with dialog boxes or a calendar (here’s looking at you, Windows), and it just works as expected. I think that’s exactly what a user interface should do. And it’s not bad to look at, either, which helps uphold the aesthetic-usability effect.