According to Neowin , MS is going to release the Rollup Update (code names Emerald) to MCE soon, which will incorporate:

  1. 2x HD Tuner supported
  2. No CableCARD
  3. No QAM
  4. DVD Changer
  5. Xbox 360 Extender support
  6. Sonic DVD Burning fixes
  7. Slight improvements in Media Library performance

The update will be free and available via Windows Update.

MS also released some information at the PDC about Diamond (Windows Vista MCE) and Neowin has some screen shots on their site and some more pictures here .