@AL, yeah it's for SL 2.. and it seems quite similar to what is being show for SL3. However, let's see how extensible the navigation system is in SL, because the MVC type routing engine that I have is quite quite powerful and extensible. Let's see..
Funny you should ask if their is a routning engine a la mvc in SL to handle the routes? That is the almost exactly the title of my blog post today.. I introduce a rounting and navigation framework based on the same api as mvc in silverlight.. check it
http://www.orkpad.com/Blog/post/2009/03/10/Silverlight-Routing-a-la-MVC-Routing.aspx (.) In my internal usage, it is awesome way to design applications because you can extend and change without have to bring down the whole house. Cheers