Thought I would post up another sample I made a while back - a 3D rotating user interface, similar to that in the Healthcare demo.
In this simple sample, there are two levels of navigation. Moving from level 1 to level 2 will rotate the main user interface away into the background, while the secondary UI appears in the foreground. See below...
As you can see, there was no expense spared in creating a compelling user interface! But this is a very simplified example on how to do this.
Although you should be able to see the technique used in the attached source code, here is basically what is happening... There is a 3D viewport in the background containing a plane mesh. The mesh has a Visual Brush as a diffuse material. When the user navigates to the secondary level of the UI, the main UI's visual is copied onto the meshe's material, the mesh is then rotated into the background. I then move the real main UI, 2000 pixles to the left to get it out of the way. Simple.
Have a play and let me know your thoughts.