I've quite amazed by the new audio stack,
though,I miss :
* to be able to output to my both soundcards at the same time ( thinking about playing same music for different rooms connected to speakers and HIFI amplifier )
* use a per display based sound config so if I move wmp on my video projector it outputs on the hifi amp and if wmp is on my lcd screen, the sounds pops out of desktop speakers.
* Control of surround (PRO LOGIC 2, AC3) so I can get the center chan on center when I'm using spdif output with my audigy 2 zs (no ac3 live encoding) or the nforce live ac3 encoding. Though I'm not sure it's windows dependant.