For those that Xbox 360 as a Media Center Extender with Windows Vista, you should note the following:
Support for Xbox 360 as a Media Center extender is not included in this Vista build. In order to continue using the Xbox 360 as a Media Center Extender with Vista, please remain on Beta 2 (build 5384). Support for the Xbox 360 as an Extender will be available in a future Vista build.
It does not appear that this build will be available for the Consumer Preview Program. This can be confirmed here, where it is stated that:
When you register for the Customer Preview Program you will receive the Beta 2 release plus Windows Vista Release Candidate 1 (RC1) — the next major pre-release of Windows Vista — when it is available later this year.
Media Center, Extender, Microsoft, technology, Vista