I probably don't get as deep into Sonar as you do Beepster, but I give it a good whirl every day. I've not had a problem. That said, just a start screen sniggle and some other minor stuff are ALL the problems I've really ever had, so I've never hesitated to update as soon as they are out. I keep garbage off my computer and don't load the latest free VST either. Also a StudioCat computer.
That said, I can do an Acronis re-install in a very short time. My 100 gig .tib files only take about 10 minutes to make as well, if going to an internal drive or a USB3. I typically never update, but just make new files and ditch the old.