Flew all legs of YYZ-PTY and PTY-MDE in J last week. Things started out crappy, as Copa did not have a prefermember lane for check-in at YYZ. The line was 50 deep, so opt'd to skip the line and carry on my 1 piece of luggage. Service inflight was the bare minimum (boxed pasta with roast beef sandwich and water), though I was given a stella when requested. Almost all flights were 3/4 full except for the return leg PTY-YYZ which had 42 passengers total. Since the Copa Clubs in Panama and Medellin are closed, I had to burn 2 of my priority pass vouchers from my credit card to access the alternate lounge, which of course, were slammed with people.
I bought J to qualify for *g in 2021, however, I would strongly recommend against paying for a J fare with Copa in the current enviroment as its basically business class pricing for an economy-level experience.