I think the true potential of Kinect and it's 3D realtime tracking ability will lie in marketplace apps. Thousands of new applications with minority-report-style UIs can be built to do everything from internet browsing to trying on clothes at your favorite stores to video editting. The possibilities are endless.

What app would you design?

I would create a dressing room application filled with the latest styles from dozens of popular stores, allow the user to try them on in 3D and then quickly make a purchase. I could see this being quite the killer app for shopping...