I have an 820. When it works it is a pretty great machine, however there are a lot of issues. Pretty easy to find bad/unhappy reviews. Some design decisions were not so good and were discontinued in future models. There were apparently some manufacturing quality issues as well and some of the machines are lemons. I don't think mine is a lemon but I have named it "Cranky Bernie". In the 7? or so years I've had it, it has been in the shop for a total of a year! That didn't include the year it was non-working during covid, and I have spent over a thousand in repairs and cleanings etc. Last couple of years I had problems with the upper thread sensor. Replaced it once, it failed after a year. Fixed it again and the part fell apart almost immediately, that was replaced for free but still took a lot of time. Currently my bobbin sensor is bad -- I've turned off that feature and it is working (before I turned it off it would not sew at all). Cost for the part is roughly $100 plus labor and again, time.
When Cranky Bernie is working there is a lot to like! Yes, huge deep throat/work space, I can quilt up to twin size very easily, haven't tried queen or larger but the space is there. Nice stitch quality and variations (I use the serpentine a lot for quilting down). Well lit. I have no problems with the needle threader. I like the knee lift for up/down. Fast, quiet -- all sorts of good. I like the integrated walking foot.
I think the price you are looking at is very reasonable, otherwise I see them still going for about 3k US.