Different people react differently. It also makes a difference where you have the surgery done. Not all do it the same way, with the same level of competence.
I had full knee replacemnt surgery 5 years ago. Regained almost full range of motion, maybe 1-2 degrees less than my other leg. I kneel all the time without any pain, though I don't sit on my heels. Getting up and down from sitting or any other position isn't a problem. I still use climbing stands and hang on stands and steps.
My repaired leg is at least as strong as my other leg.
In short, for me, I can do everything I could do before the replacement, and a lot more now that I'm not dealing with the continual pain. On the other hand, my neighbor, who had a knee replaced about the same time, suffers from most of the same things that joe does.
I'm very grateful. Given the shape my knee was in before I had the surgery, I would choose to do it again, even if the outcome were less positive.
I would add, get your leg muscles in as good a shape as possible before surgery with a good exercise program. Your clinic/hospital/surgeon should have one to offer. Then, rigorously do all of the rehabilitation exercises after the surgery.