Just filled out the survey -- I've had the 8XX since Nov 2021, and just got the 800S from Adorama via UPS yesterday.
The comfort of these is slightly confusing to me -- they are super lightweight, for sure, and the ear cups are big enough for my sizable ears so my ears never hurt, and I don't get any hotspots on my head, but I don't "forget" I'm wearing them -- somehow I feel them on the side of my face and it's slightly, minorly distracting at times -- but that's when I'm being super critical because I've never NOT picked up these because of comfort.
Oddly enough, though the clamp is definitely less than my HD 600/650/660S, I find those because of the shape of the ear cups and the plusher earpads, slightly more comfortable, and I know a lot of people can't stand the clamp of those.
The stock cables are super long, but I don't mind it that much -- and if I did, I would just buy an aftermarket cable, but I find it a high-quality cable and also -- I've never pulled the 6.35mm cable out because of the fear of having difficulty not damaging the headphones, from what I've read, so I've never attempted to use them balanced, although I suspect I will at some point with these 800S since it came with one in the box.
As far as the sound quality, while I definitely appreciate the wide soundstage, the jury is still out for me on whether I find that more compelling than the more dynamic, punchier Focal Clear -- I listened to the 8XX more when I first got them but have picked up a number of other headphones since then, but only recently again picked them up again to reacquaint myself with them in preparation for the 800S which are on my head now.
I'm curious as to what Sennheiser might do next in this space, but I'm actually probably happy enough with what I have that I'm certainly not in a rush to "upgrade", having just done that going from the 8XX to the 800S.