Following BUILD, there is still some angst surrounding Silverlight and the role it will play moving forward. This is understandable after hearing that Silverlight does not run inside the Metro-UI IE browser. There are good reasons why supporting Silverlight under the Metro-UI browser is not a great idea and I believe that Microsoft was right to stay away from it.
Microsoft released Silverlight in 2007 in order to: (1) make rich Internet applications (RIA) easier to deploy and (2) enable cross-platform development. Silverlight achieved its seamless deployment goal. However, since cross-platform adoption never panned out, Silverlight became a de facto Windows only solution.
Moving forward, I believe Silverlight only makes sense on legacy projects. If you are starting a new project with Silverlight, you should evaluate all available options. It is a good choice only if deployment concerns are paramount (XBAP deployment is not as seamless as Silverlight). Even when deployment is your primary concern, definitely consider an ASP.NET MVC solution as an alternative option. There is excellent tooling support for ASP.NET MVC and you can be very productive. You get excellent deployment characteristics and a cross-platform mobile story.
In all other scenarios, I believe WPF is a much better choice for a desktop UI. You can stick to a subset of WPF and produce a UI that looks great and offers excellent performance while sharing code with its WinRT twin. WPF will easily out-perform Silverlight (especially when dealing with large amounts of data) if you take advantage of WPF-specific features such as support for lower level rendering primitives (this is one of the reasons that not all of our WPF and Silverlight controls share the same code).
Syncfusion will keep adding functionality as well as supporting Silverlight. Our XAML team is integrated; most functionality will continue to be added to both Silverlight and WPF. Syncfusion has always maintained separate WPF and Silverlight codebases when it comes to solutions that required deep integration with WPF (such as the grid and chart controls). These controls will be independently enhanced for newer versions of Silverlight and WPF.
Interested in more of my post-BUILD analysis, read my latest whitepaper: “Windows 8: What it means for development decisions today and in the future.”