I get asked about this quite a bit, so this is session from PDC is a ready-made answer 🙂
Over the course of the session Ian builds a Twitter client in both Silverlight and WPF highlighting the pros and cons of each approach, what code is the same and what is different and why. Ian covered many details of Silverlight and WPF compatibility as well as the philosophy behind the approach taken.
The session will help improve your understanding of the compatibility between Windows Presentation Foundation (WPF) and Silverlight, and you'll learn the relationship between WPF and Silverlight's various subsystems including: XAML parsing and serialization, control instantiation, styling and templating, layout, rendering, and more.
Cross posted from Ronan's blog