Major Nelson brings word that there will be an auto-update for those owners that have the HD DVD drive. Improvements include audio output selection, improved parental controls and 1080p via HDMI with an Elite.

++++++++++++++
From the release:

Added option for user to select from the following audio output formats via TOSLINK or HDMI:
o Digital Stereo (2 channel PCM)
o Dolby Digital 5.1
o DTS 5.1
o WMA Pro
Added "Dynamic Range Control" toggle for digital audio output
Improved HD DVD networking support
Improved HD DVD title compatibility
Improved performance with MPEG-4 AVC / H.264
1080p via HDMI is supported on the Xbox 360 Elite with HDCP compliant displays
Improved parental controls