Hello, I can share my experience...I own lumia 1020 from 8.1 to redstone. I didn't notice any degrade in photo quality overall, it changed in some way the white balancing in win 10 but I don't think It can be considered a degrade. Moreover you can still use lumia camera with all your functions, because for 1020 It's still downloadable. What is not so good is the time for taking a shoot, in some situation I think it's slightly increased and this behaviour in some situation is annoying. Another little bug is that sometimes when you first launch camera app, the first photo tales ages to finish (20 sec...). This doesn't happen always and after the first photo the other work good: A little trick is to maintain the camera app reduced and then sometimes activate it again, when you know that you'll use it a lot.
Overall I'm satisfied of my experience and I would buy it again, and I still think it's the best camera phone on market...
Hope this help...