Hi,
It IS much better quality than standard analog FM and AM radio but unfortunately it took many years for the industry to select and standardize a system that didn't cause interference to the analog AM and FM signals broadcast on the same channel.
The system chosen carries the digital signal on a sub-carrier frequency, which is extracted and decoded for playback. It works, and so far I have not come across reports of interference between the digital and analog signals.
When I lived in Toronto, the Canadian Broadcasting Corporation (and some commercial broadcasters as well) experimented with a digital terrestrial radio system based on a European standard called Musicam. I later did listening tests with this system and it was excellent, but it never materialized because the broadcast frequencies conflicted with some military frequencies in use by the Pentagon. . .
I have not done in-home tests of HD radio, but you might find some reviews by critics I know if you Google HD radio or check on CNet.
Regards,
