My friend who had the 820 before me replaced it with a 770 and loves it. Not everyone likes Berninas, but Bernina owners seem to love their 770s -- while the 820 is generally not held in such high regard.
Mine's in the shop, they have just reopened after Covid. They just called and it will be ready in about a week and the estimated cost is less than I had expected (a little over 200 instead of the $350 I had figured).
Woohoo! I've been sewing on a bottom of the line Brother and I had gotten used to the bells and whistles of the Bernina.