Quote Originally Posted by stlowe
.... Not only does XAML allow you to use the same UI for both WPF (for desktop apps) and silverlight (for web apps)...
....disclaimer: though I work for Microsoft as an Architect Evangelist, my opinions (and occasional errors) are my own....
Not exactly (at least in the current release) Silverlight is an improper subset of WPF. As a result (for any non-trivial situation) it is impractical/impossible to create a single XAML file that can be used without any modification for both a high quality SilverLight site and a WPF application.

FYI: I am a former MCS Sr. Consultant, and have had to actually implement and support many "AE" architectures and designs...