I've published the demo source for my Deep Zoom, MultiScaleTileSource and the Mandelbrot Set post to my site at http://mikeo.co.uk/cs/files/8/silverlight/entry43.aspx. I also made some changes to the colouring algorithm.
Instead of using the simple "Escape Time" algorithm it now uses a refinement knows as the "Normalized Iteration Count" algorithm which reduces the banding artifacts. The calculation is more expensive though so the zoom / pan responsiveness has dropped off a bit. However, it does look nice.
The image on the left is the result of zooming in on the tiny area highlighted by the arrow on the right.