Use Storyboards for Game Loop, not DispatcherTimer
Ok so I had some earlier posts discussing how to make a game loop using two different methods, one being an empty Storyboard, and the other being the use of a DispatcherTimer. Adam Kinney of Microsoft has researched it a bit, and has posted his findings, confirming some of the empirical results I found from testing the two:
http://adamkinney.com/blog/339/default.aspx
Adam writes:
The DispatcherTimer is a lower resolution timer than the timer behind the Storyboard class, which causes loss in fidelity. Additionally, the Storyboard execution is more stable across the different supported OSs and Browsers.
So it looks like to get the smoothest movement in your game, you should use the Storyboard technique that I talk about in my Silverlight Game Loop tutorial.