wow, i didnt know people still used HD radio.. lol we use pandora now.
the biggest problem with HD radio is that (from what i know and have actually experienced this using a JVC Arsenal years ago) it's a digital signal and unlike analog, when there is some interferrence the signal completely drops off instead of hearing a light crackle like on regular am/fm channels.
i personally think HD radio was a failure. good concept but not enough RAM in the HU. i dont know if there was ever a HD specific standard made for RAM buffering.