My wife is 13 years younger than me (I'm 40, she's 27) which works great for my livestyle. I can meet people of any age that I have some compatibility with, but in general, I usually find that people my age (present company excluded) have abandoned a lot of the things that make us feel young, so my group of close friends is more my wifes age than mine. You can have kids and mature professionally without losing your spontaneous, funloving side, but a lot of people in their late 30's and beyond (at least in my hometown) seem to lose their identity once kids come and the wedding ring is slipped on.
...... Oh.....and I forgot to mention, the sex totally rocks with younger women!!