Jeremy Likness is going to deviate from his typical "line of business" blog posts to discuss how to simplify animations with clones by using WriteableBitmap.
I've had a few projects where it's been necessary to use animations to transition between "screens" in the application. While I use the visual state manager as often as I can for this, sometimes the transitions aren't really changing the state of the control itself, but simply animating the change of underlying data.