A refreshed version of the Windows Vista Media Center SDK (version 5.2) has been released for download.  The download location is the same as the 5.0 and 5.1 versions - http://www.microsoft.com/downloads/details.aspx?FamilyID=A43EA0B7-B85F-4612-AA08-3BF128C5873E&displaylang=en.  If you have the 5.0 or 5.1 version of the Windows Vista Media Center SDK installed, you can run the MSI for version 5.2 and it will automatically upgrade the older versions for you.

The features of this SDK refresh are described in more detail in this post on the Media Center Sandbox blog and also in the Getting Started page that appears at the end of SDK installation.  The key changes are the following:

• The contents of the Media Center Application step-by-step guide that was previously released as a standalone document with source code has been incorporated into the SDK documentation
• The C# project template included with the SDK has been greatly enhanced - it now creates a more interesting application based on the source code of the step-by-step guide.  This will hopefully make it easier to get up and running with MCML and C# code behind for Media Center applications.
• The C# project template also now includes WiX 3.0-based setup source files to make it easier to get started creating an MSI-based installer for your Media Center application.  These files appear in a setup sub-folder when creating a new C# Media Center application project, and they include the necessary information to install an application assembly to the GAC and register the application using RegisterMceApp.  They also include some prerequisite checking so the resultant MSI will verify that the OS the user runs the installation on contains Windows Vista Media Center and that the user has administrative privileges to install the application for all users.  Essentially, these setup files look similar to the Q and Z sample application setup files (but they install a different set of application files).
  
  The MSI creation steps will not be a part of the build process until you hook up the post-build event to run the WiX compiler and linker (candle and light) - the steps for hooking this up are located in the readme file that opens when you create a new project in Visual Studio.
• The MCML File item template that is included in the Media Center SDK for use in Visual Studio 2005 has been enhanced to include commonly used MCML elements (Properties, Locals, Rules and Content)

If you're a Windows Vista Media Center developer or thinking about getting started, I encourage you to download this new version of the SDK and check it out.