I think all the posts here are relevant to feminism. Talk about ageing with regard to women, and you get a whole bunch of guff about losing your looks (er, I still have looks, thanks; they've changed but not gone away) and still being able to fit in your wedding dress (well, that must be handy if you're thinking of using it again). Men, otoh, might mention a decline in their golf swing but generally take the view that they're still great if a little creaky here & there.
It boils down, yet again, to women's appearance - which now includes fitness and perkiness, as well as facial smoothness and poutiness - being the most important thing about them. I'm in the school of ageing women who find the "loss" of youthfulness about as irritating as your male golfer does but, on the whole, enjoy new freedoms bestowed by age. Am I supposed to look at 30-year-olds and wish I had their looks, or were as lithe as them? Tough - believe it or not, I have been thirty; had my turn, and now I'm doing something different :)
Ageism, in terms of employment and financial opportunities, does piss me off. The beauty thing, not really. It saddens me to see women all over the place "dreading" ageing, purely in terms of appearance. I loved what somebody wrote, above, about being able to look forwards AND back!
As a feminist, I'd like to see our culture acknowledging the realities of ageing more positively. I think it will happen - I'm in the early part of the baby boom, we're still the biggest chunk of the population and our collective spending power has actually grown. The ad agencies who embrace these facts constructively will make a killing. (If they can bring themselves to hire someone over 50!)