While I don't use Pt anymore, I wouldn't necessarily call Yosemite a POS OS. Yea it has bugs, however I have no probs running my audio apps (logic/cubase/ableton). Like @simonsi said, people need to have a procedure when updating the OS. When Yosemite first came out, I waited til .1 was released....and even then I still waited a while before installing it cuz I wanted to see what everyone else's experience was. I made a backup of my previous OS version (Lion), then updated. I made sure it would run fine before making the decision to keep that version on my MBP.
If you rely on your comp as your source of income, whatever it may be (audio/video/etc), then you need to be more weary of what you're getting yourself into as far as stability. Don't update cuz of "cool features" or "I need to be on the cutting edge". If the OS isn't working the way you hoped it would be, then restore back to your previous OS. That's what TM is for.
Now for those who bought new macs that had Yosemite preinstalled, I feel sorry for them since they can't do anything about it. However, assuming those people already had a Mac and decided purchase another, then they should go back and use they're older Mac (assuming it didn't have any probs). Maybe update the HD on the older Mac. My late-2011 MBP runs Yosemite just fine w/ 16GB of RAM....and I don't even have an SSD installed yet.
That being said, just because one user has a bad experience doesn't mean everyone does.