I got my 816csx through a Yamaha half-price Loyalty upgrade when they discontinued support for my Yamaha 01x. As far as I know, they haven’t ‘officially’ ended support for this unit, just unofficially.
Mine was working as well as it ever did up until I took it out of my workflow last week to install a UR-RT. I had to rethink a good bit to retain the functionality I had enjoyed. My 816 is still in my system, used ONLY for passing audio out to my live room speakers via S/PDIF optical. The UR doesn’t have a S/PDIF of any sort.
The stupidest mistake they made on the MR816s, IMHO, was that the S/PDIF in could ONLY be recognized as a Stereo input for the dsp. If you tried to run two mono channels through it, as I did, the dsp, didn’t connect and the direct monitoring didn’t work correctly. I still think SOMEBODY at Yamaha should have anticipated that some of us would want to use it that way. Of course, not being able to daisychain properly was a bigger problem, because they advertised that you could.