Joel Neubeck is talking about using WritableBitmap for smooth transitions between the pages using Navigation Framework:
One thing that i thought was missing was the ability to create nice looking transitions between pages as they are loaded into a frame. Recently I voiced my complaint to a coworker and he had the great idea of using a WritableBitmap to capture the current and next page within the Frame, than animating the images. Here is the solution I arrived at.