As the ability for the switches grow in frequencies, which is happening, the ability for these amps to be used in high quality settings are becoming a reality.
I talked to my father about this today. He is an electrical engineer, 55 years old, and was building amps and receivers when he was 13. He knows a bit about audio, though he hasnt done much with Amps, Short Wave, FM, or AM receivers in a long time.
Anyways, he told me they been using these by DJ's for years in professional applications. Probably to power the lower end subs. The future is happening because of more and more micro engineering, or even nano-tech if you want. Though that term has allot of stipulations to it.
The D-Class amps should become the best things on the market. Time period for affordable high quality amps seems to be short, but I would assume that if you bought a high quality tube or solid state amp now, that when the thing is old or time to upgrade will be about the same time that these D-Class amps become affordable at high end quality.