> The sound quality is surprisingly good. Now I understand why people were complaining when they moved from AMPS to the first generation of GSM — the FM with 12 KHz modulation works actually well.

I remember this. When digital voice became commonplace a frequent complaint was how people sounded like they were underwater from the compression. I don’t think it was until VoLTE became a thing that I can recall a really big increase in voice quality since the move to digital voice.