I for one am thrilled to learn that with the new update rolling out to U-verse customers (New Total Home DVR and guide/menu visual update) you can now stream Dolby Digital 5.1 surround sound to your audio/video receiver!!
This new option is not enabled by default. You will need to go to Menu>Options>Language/Audio Options>Digital Audio
Your choices will be Stereo or Surround. Pick surround, go back to start test, and you should shortly thereafter see the correct indicator on your AVR (if available), you should also immediately have surround sound if available on the program you're currently watching.
I was watching "Brothers and Sisters" from my DVR and it worked flawlessly.
Remember that if you have your AVR set for Dolby Pro-Logic or similar, you might need to remove that to avoid additional processing from your AVR.
Finally, I'm not sure if this affects those customers using the Cisco DVRs/STBs. We have the Motorola DVR.