Most of the big pros and cons have been mentioned already, but for me, it's the eyes. Yes, the knees don't work well, etc., but I'm afraid of what is going to happen when I can no longer see well enough. Crappy hearing isn't fun, but doesn't effect the photography much, but it is already difficult to see some things. By the way, young ones, be aware that the amount of time it takes for the eyes to focus on something drastically lengthens as you get older. i.e., you come up to the intersection, glance one way and then the other. When you are young, that works. But when you're older, you have to look longer and multiple times to catch it all.
.... and then there's the memory .... why did I come out here today... ?