I just spent the day tooling around in a beautifully done up Bonanza (brand new panel--sweet). It had the DC retrofit ANRs in it (the owners), so here's what I saw:
They really were quiet. They were heavier than my DC headset (dunno what model--I've had them a while)--but they were very quiet and felt like every other pair of David Clarks I've worn. So, there's what I know about them from my limited experience.
Dan
Although, for the record, I'm not about to go out and drop the cash to retrofit mine--I'll just buy a full ANR headset