rt，姗姗来迟~
几大亮点：支持编辑功能；支持与time-enabled数据交互；必须使用silverlight 4&vs 2010&expression blend 4进行开发；要使用完整功能必须有arcgis server 10支持；支持wkt。
具体见http://help.arcgis.com/en/webapi/silverlight/help/?Whats_New.htm
what’s new：
- Silverlight 4 is now required to develop Silverlight applications. Silverlight 3 is no longer supported.
- Visual Studio 2010 and Expression Blend 4 are required when building Silverlight 4 applications.
- You can edit feature layers associated with an ArcGIS 10 Server feature service.
- The Map and layers support display of time enabled data.
- The enhanced geometry and route service operations are available.
- The API now supports spatial reference defined as well-known text (WKT).
Known issues:
- Both Silverlight templates may return an exception or blank page in the design view of Expression Blend 4 and Visual Studio 2010. To resolve, add a reference to the System.Windows.Controls.Data.Input.dll (in <Program Files>Microsoft SDKsSilverlightv4.0LibrariesClient) and refresh the design view.