I found a nice article on "Silverlight for Symbian hits 20K download" The blog states that the "Silverlight for Symbian – Beta hits 20K in successful downloads". Silverlight is the development platform for Windows Phone 7 along with the XNA Framework . Microsoft had announced a Beta version of Developer Tools and Silverlight runtime during the MIX'10 to enable users...

Recently , Microsoft announced the release of the Windows Phone Developer Tools CTP .The development platform for the applications are Silverlight based .The GUI looks good and clean too.The runtimes supported are Silverlight, XNA Framework and .NET Compact Framework ....