I think the reason the HD channels - OK, let's just call them digital radio, shall we - don't stand much of a chance of gaining an audience is because the FCC lacks the balls to use its power to regulate. If all AM radio receivers in the US must go up to 1700kHz now, since the expanded AM band was initiated (and hasn't that made such a difference?), then why in the world won't they mandate "HD" digital radio capability on all receivers from here on out?
Same thing happened with AM stereo. The only time I ever got to hear it was once in a rental car, years ago, and I was amazed by how much better the music station sounded from routine AM. Couldn't ever get it on the in-dash radio on the cars I bought, since few of them had it.
These new technologies can help address the shortcomings of the radio industry, but not if its a "no, you first" Seattle-style four-way stop kind of thing. (see Pemco commercial for that reference, if you don't experience it yourself on a daily basis around here.) Consumer demand does not happen 'organically' when the technology isn't there in the first place, and there are scant few stores where you can find educated staff to sell you the kind of radio you really want anymore.
The irony is, the country-club republicans at the NAB who decry any kind of "regulation" on the part of the FCC (again, see where that's gotten us all today) are too blind to see how having a few more government-mandated rules, at least for the technology, sets the stage to benefit everyone, by creating a level playing field.