I tried watching a movie on there the other night and it was not good. It was LB format and made it about 10 to 12 inches smaller than my TV screen.
A secondary negative about SD channels is that they do not supply Dolby Digital sound.
They could. Prior to the launch of HD, many of the SD movie channels were in Dolby Digital. My first DirecTV receiver was an RCA with DD output circa 1999. All channels were SD, but there were a few channels with DD sound.