I have been entranced with literal transparency since the days of Gibson's "Neuromancer". I love the concept of tunneling through black ice, or sifting through clouds of information that exist in virtual file cabinets in Crichton's "Disclosure" or the visuals of 3D navigation with "Minority Report."
One of the key features of Ubuntu with Compiz that I use significantly is the transparency feature. You can set windows to be transparent when you move them. However, simply by clicking on the title bar (or activating via hot Keys) provides the ability view below the application as you see in the screenshot. By clicking on the title bar of Microsoft Word (running via Wine), I am able to see the web page in Firefox. I use this functionality more than any other feature in Ubuntu.
This is 10X. I now have the ability to look at my information transparently. I can't replicate this act in real life. How many times have you scrambled around your desk looking for that paper that you had in your hands 5 seconds ago? How many times do you jockey between 2 pieces of paper to build a memo or report? How many times do you alt-tab between 2 screens?