I've known three people that had them done and the one thing they all said is they wished they had done it years earlier.
None of them are doing any athletic pursuits but that was never their thing to begin with. They were all overweight and didn't exercise--two things that likely compounded their issues IMO. Anyways, they are happy now because they are able to go on walks, do housework, and live their lives without having to ice their knees and eat bottles of painkillers.
Pellius I assume you are in the market for a knee replacement? Is this from osteoarthritis or some old accident?