I had bad experiences with Bryston, which was surprising, given their reputation is the opposite.
I had bought a ‘factory refurbished’ optical reader. It ripped 2 CDs, taking about an hour each, then died. Bryston had me pay for the shipping. When it came back it was worse. They again asked for me to pay shipping charges. I complained, they were inflexible, I sent it hoping that given their overall reputation that this would be an outlier, and it came back completely dead. They obviously don’t test their ‘restoration’ work. I used it as a doorstop for a while.
I also owned the BDP-3 for a year but found it a terrible component because of the software (mis)management system. However their CS did try to help, it was just that the component (which actually sounded excellent) was flawed in conception.
I love Bryston DAC3 and have had no issues with it, and also owned a second hand power amp that worked great until it was stolen. However I never need to ask for CS on either of those components.
Second worse CS I ever had was Rega. I had bought an external speed stabilizer for a P-5 turntable. It died after about 5 months. The dealer sent it back over the pond for repairs. Months and multiple inquiries went by. Finally after 7 months Rega said it was out of warranty and they couldn’t do anything.
On the excellent CS side I had wonderful experiences with Cary Audio and Prima Luna