You must be living in an area where there's good reception and no HD2/HD3s of interest.
There is an improvement for me, not only in sound quality, but also station selection. For a station that I receive without multipath distortion, there is no improvement. However, whereas some analog stations are fuzzy sounding (sometimes clear one day, fuzzy the next), when the HD stream starts for that station in a second or two, it clears up to perfect audio. Here in Denver, there are some stations that have terrific HD2 and some with HD3 streams, both classical and oldies. I left terrestrial radio about 10 years ago because of obnoxious DJs when I wanted music, tons of commericals, and unreliable reception. HD has brought me back.