Yes, I perhaps failed to state one very real advantage... due to the advanced codec and fairly generous bitrate of HD Radio it will pretty universally sound sup

Yes, I perhaps failed to state one very real advantage... due to the advanced codec and fairly generous bitrate of HD Radio it will pretty universally sound superior to analog FM (unless there's something going wrong somewhere). That said some stations do make the decision to run their HD2 at a much lower bitrate that results in reduced quality, but usually that's done when their HD2 is talk or news programming only, and HDC at low bitrate handles voice pretty well even if it does get some noticeable raspiness in the high frequencies. Because radio tends to have such a bimodal distribution between "mostly music" and "mostly voice" I wondered if there has been work done on using a dedicated speech codec such as CELP or a derivative, but I think that in practice AAC (which uses the MDCT method that is also common for speech coding) performs well enough for low-bitrate speech that a dedicated speech codec would not gain a lot of efficiency or quality. Moreover, since decoding was to be implemented in hardware having any radio station using a different codec would end up driving up the cost of receivers... People tend to look down on HD radio when I saw "98kbps typical" but it's important to realize that HDC performs very noticeably better than MPEG 1/2 at those bitrates. It does not sound like a <100kbps MP3 would. Unfortunately, probably due to the low adoption of HD radio receivers it seems surprisingly common for radio stations to have quality problems with their HD audio due to misconfiguration. One station in my market had some kind of failure that resulted in no audio at all on their HD feed and it persisted for over a week.