Silverlight 4

Question :: What features are missing from Silverlight presentation markup that will be supported in the Windows Presentation Foundation?
Ans::Microsoft recommends the Windows Presentation Foundation for building rich immersive applications and experiences that can take full advantage of the Windows platform, including UI, Media, offline communication, OS integration, Office integration, peripheral access, Document support and more. Silverlight will be used for broad reach interactive media content and browser-based rich interactive and high-performance applications and experiences.

Question :: When would a customer use Silverlight versus Windows Presentation Foundation? Is Silverlight for a certain type of application?
Ans::For ASP.NET-based Web applications, Silverlight provides a rich UI front-end that, with a consistent programming model, adds support for richer interactivity, media, and audio.
For Microsoft SharePoint–based content, Silverlight offers the ability to create rich Web parts. For Windows Live services, Silverlight offers the ability to consume services and APIs more effectively.

Question :: How does Silverlight make the Microsoft development system better?
Ans::Silverlight is a cross-browser, cross-platform plug-in for delivering the next generation of media experiences and rich interactive applications (RIAs) for the Web.

Question :: When would a customer use Silverlight instead of ASP.NET AJAX?
Ans::Silverlight integrates with existing Web applications, including ASP.NET AJAX applications. Consequently, ASP.NET AJAX and Silverlight are designed to be complementary technologies. In the broader sense, Silverlight can talk to any AJAX application, both client-side and server-side. ASP.NET AJAX can additionally be used to control Silverlight-based visualization of data or delivery of rich experiences. Examples might include mapping applications or video playback with rich presentation.

Question :: Are the features of the Macintosh and Windows releases of Silverlight fully compatible?
Ans::yes