I have the Yamaha IBOC receiver RX-V4600 as well as an automobile IBOC
radio. On FM here in Detroit, there are about a dozen stations
transmitting second "HD" programs which are of greater interest to me
than the "main" channel since the second channel programs offer music
choices that aren't particularly appealing to the huge radio
conglomerates (clasical, swing album-cut rock etc).

On AM, IBOC is very problematic because it doesn't really offer
anything to the AM broadcaster, and is of minimal use to the listener.
The fidelity is quite poor on the three IBOC AM stations that we have
here in Detroit. In addition, an EXTREMELY strong signal is required
to receive the IBOC "carrier" and as AM fades or experiences weakening
signals (such as going under a highway bridge), my car IBOC receiver
loses the "digital lock" and annoyingly reverts back to analogue.
Thus, the "promise" of distant stations being "cleanly received" in
digiital mode is not fulfillable using the IBOC system. I think that
the AM IBOC will fade quickly away. The FM IBOC does offer
substantial benefits for the listener due to the multicasting
possibilities.