When I first started using Mac OS 10.3, one of the new features, Exposé (which causes open windows to fly around the screen to show all open windows, the desktop or the open windows of the current application by using a hot-key) looked really wizzy, but I didn’t think it would add much real functional value.
I was wrong. I find that I use the feature all the time, particularly F10 (which shows all open windows of the current application). It makes it so easy to navigate around an application, particularly those with multiple windows (I use it a lot with Thunderbird, mozilla.org’s email client, and Logic audio, my audio recording package).
I use F11 (show desktop) occasionally, and F9 (show all open windows) less again. But when I do use these options, it’s a great time saver.