Jamie Cansdale of Test Driven.Net has improved the Reflector Silverlight Add-in and started a community project here. If you have improvements, bugs, or features request please posted them to the community site.
Jamie changed it so that the C# or VB doesn’t get displayed in tabs by defaut as this doesn’t scale well for larger projects. You can still digg through the code as the assembly is added to Reflector. He tested against all the samples on the Silverlight.net Site and found that the add-in didn’t scale well for the airplane sample.
Jaime also has done some great work on integrating unit testing with Silverlight .NET that I would suggest checking out.