I don't look my age at all, and am often taken for 10-15 years younger than I really am. Which I thought was great until a much younger woman pointed out that unless people admit to their real age, other people won't get a sensible view of what people that age are really like. So for example we have a stereotype of what a 50 year old woman is like - and that will never change unless the women who don't fit the stereotype actually tell people that they're 50.
Is this a feminist issue? I don't think men have as much of a hang-up about their age.