It has been a week now since I put my AppleTV in its box and took it back to the Apple Store. Unfortunately, I was told I needed an appointment to receive an audience with a “Genius” in order to get it seen to, and nobody was available. Since this involves a 45-minute drive through the West Island’s lethal road construction, I haven’t been back yet.
The upside is that I have had a week without an AppleTV in my system, and during that week AirPlay playback has been flawless, provided I followed the (revised for Yosemite) procedure I described last week. That’s three systems - a 2014 RMPB, a 2013 bare-bones Mac Mini, and a 2009 MBP. All running Yosemite, all working just fine, first time, every time, with AirPlay.
I thought that was worth reporting.
I now have my new AppleTV from the Apple Store. To find out what happened when I installed it in the system, read on here.