I guess I have been really lucky ...
Had my Cary slp98 preamp upgarded and they did extra things for me at no charge and right on time, Had tech questions on my Cary 200ts DAC and responses within 24 hours. In my office I have Emotiva monoblock xpa1s that were having a few issues just before the 5 year warranty ran out, not only did Emotiva fix the issues but because they determined some other things that would eventually fail a long way down the road, they replaced the caps etc all at no cost and within a few days.
I recently purchase a set of Odyssey Kismet amps from Klaus, the left amp came with an issue due to shipping, not only did Klaus replace the left damaged Amp he upgraded it and so it would match replaced the right amp. That is what I call customer service at its best. Maybe it's luck, maybe it is picking the right vendors, I don't know but within certain limits I am a tough to please person and all three of these firms have been exceptional in service. You can argue sound quality, micronuances etc, but service is not subjective it is an actual event and these firms performed above and beyond.