My C658 has seen improved stability since the early days. Not perfect, but liveable. Once or twice a month I have to deactivate the wifi connection and turn it back on. Optical cable sometimes takes a few attempts to sync with my CD player (it sometimes pops and clicks during the first few attempts of the day but then it works). I don't know if the CD player or the C658 is to blame... Annoying and inexcusable, but completely usable. My sub outputs are fine.
There was also some retuning of the DAC at some point and the self-noise in my sample was greatly reduced based on unscientific testing by turning up the volume and listening for noise during quiet/silent passages.
Between the tone controls, sub outputs, streaming, BluOS connectivity for distributed audio, optional HDMI input/output, and Dirac Live it's a one of a kind box and I still recommend it... Despite feeling some resentment at NAD for their shoody engineering and QC.
Do I wish it measured better and worked flawlessly? Of course! Do I wish it was $1000 less fully loaded with HDMI? Yes.
But most importantly, when paired with my M2s does it still manage to produce stunning music that can captivate me for hours with incredible convenience and ease of use? Yes.
