In terms of reliability, 5 out of 5.
Sound quality on their DAC's has been iffy but I think has gotten better.
Any opinions on NAD quality?
As with nearly all listeners, I believe the NAD sound to be just about the tops for the money expended. However, I have heard reports of quality control issues (nothing specific) to the point of being much worse than other manufacturers. Along with a lot of other audio equipment, I own a NAD c 740 receiver, less than a month old, and so far it's working quite well. Still, I wonder what's ahead.