3D desktops have been tried in the past with limited success. Maybe interfaces like this will finally allow a UI to be developed that utilizes the z-axis so more can be packed into a limited space.
Bas is right though; it may be too much for users to handle for general purpose uses. Just look at people's reaction to the changes made to Windows for W8 -- not great. Then again people seems to take to the Kinect pretty quickly.