The majority of my 30+ Dish HD stations offer 5.1 DD sound. I just did a quick check at 12:50a.m. and 26 stations were broadcasting 5.1 sound and the display indicates "Dolby Digital" on my receiver. (When I receive a PCM source it indicates "PCM" or LPCM" like from my lossless HD audio codecs over HDMI.)
Part of the reason that Dish offers so many more DD5.1 channels is that all of their VOOM channels (over 15 of them) use DD5.1 all the time.
As to the quality of the audio, it sounds fine to me and I'm using pretty good equipment for sound reproduction. I would rate it equivalent to most DVD sound, but certainly not as good as the lossless audio codecs, like TrueHD, etc., of HD/BR discs. However, that's an unfair comparison since lossless audio has a much higher bitrate (on the order of 6.9
Mbps) compared to DVD audio (usually in the 448/640
Kbps neighborhood.) That's certainly not a level playing field.
