Overall, a lot was expected from High Definition Audio, but a lot of it wasn’t delivered. Still lacking is Dolby Pro Logic IIx, better Jack Sensing/Reassignments, better DAC’s, and 32 bit/192 KHz support. The limitations of High Definition Audio seem to stem from the UAA drivers. Simply put, UAA wasn’t designed for Windows XP, getting UAA running on Windows XP was a hack job, as it was designed with Longhorn in mind. This could explain the lack of Dolby Pro Logic IIx support. Sure it’s a massive improvement over existing ALC650 equipped audio solutions, but that’s not saying much.Seems a little harsh to me. Nearly no source audio out there is 32 bits, and I was pleasantly surprised to find that Realtek's codec would do 24 bits and 192KHz on all eight output channels with a decent signal-to-noise ratio. I guess it all depends on one's expectations. My ears also didn't detect an egregious quality drop-off between the M-Audio Revolution 7.1 and HD Audio in my informal listening tests, but then the headphones I was using weren't the greatest.
Update: All right, I just did another quick listening comparison, and the Revolution 7.1 absolutely owns. With the right music, the clarity of the Rev card is obviously superior.