Why? Because even though Silverlight has a super-cool UI model, gives you mini .NET framework, and let's you program in C#, it still can't give me what I really want: my domain objects. So now I'm using ASP.NET MVC, and I'm loving it. I can build a clean, testable UI layer that leverages the full power of my domain model. Add in some jQuery for AJAX, and I can leverage the client to get partial page updates while still leveraging the server to generate the UI. From my perspective, a beautiful compromise.