As a long-time HD user, here's my experience.
This format was conceived as a way to increase program content & signal purity. Individual transmitters had to upgrade to digital format at their own expense, but this opened up the capacity for multiple formats broadcasting simultaneously. I.e. wksu, the regional npr/public radio broadcaster in my area has 4 separate channels running on the same frequency, 4 different formats. Npr news, a folk music sub-channel, classical music sub-channel & a dedicated news feed. Not blowing their horn, just relaying HD capabilities.
This mode is not flawless, however. To decode the digital stream, a strong received signal is required. If you live in a fringe area as I do, an external antenna is mandatory. (I have a rotatable 6-element yagi & a crossed dipole in the attic). If youre in an urban area, this is not so much an issue, plus there's more stations to pick from. Like digital terrestrial tv, it's either there or it ain't. The first radios on the market weren't very sensitive, & it could try ones patience putting up with constant drop-outs. HD receivers also function as conventional radios when not on an encrypted frequency.
Along came Sony's xdr-f1hd am/fm HD rig, which rewrote the book & pretty much set the standard for HD receivers. This tuner, which is just that, now costs more used,if you can find one, than when new, such is its reputation and resulting demand. It also out-specs & out-performs most conventional tuners. Unfortunately, no longer in production, so if you can find one,especially for $100 or less, grab it!
As an added bonus, HD radios have scrolling multi -function displays to indicate programming content. Hear a song ,it's on the display.
All that being said, not a perfect medium, but a great leap forward from the limits of analog broadcasting, which I hope never goes away, as it has and will in several countries across the pond.
Merry Christmas all, DE K8CAT