Virtually all of the comments on HD so far have been surrounding the technology but aside from music quality what does HD provide? You don't need it for sports, talk or any other of the myriad traditional uses of radio. So music is now a niche on radio given the number of outlets that are not radio based.
There might be a genre that takes full advantage of HD radio but if there is I haven't heard it yet. A quality analog FM signal is just fine for any music genre of my lifetime. And I am saying this as an owner of one of the finest HD/mobile sound systems yet put in a luxury vehicle. Given the physics of an FM signal, digital or otherwise, there is not a lot more the industry can do to address the only significant shortcoming - the range. AM HD is homeless so no happiness there either.
I am not anything approaching an expert on the subject but to an ordinary radio listener it seems digital radio has gone about as far as it can without significant new content to draw an audience. I would certainly not pay a penny extra for the technology.
In my metro HD offers formats that the FM stations otherwise won't run -- classic alternative, metal rock music, jazz, blues, etc. The local standards AM station is on HD FM in stereo, on an HD3, and it still sounds pretty good. They ran Christmas music and it was the Christmas standards -- the AM signal is clean, but the HD3 FM channel was stereo. So there are some things that HD provides which benefits the listener. I listen to some of the HD2 FM channels on my Sangean HDR-16. I don't listen to regular FM anymore.