They've become more accepting of their own bodies. The women can walk through a checkout line, indifferent to Cosmo Girl number 733. They remember the days when stuff like that mattered, and are able to smile at themselves. My male friends better know what they want, from themselves and others. Love becomes less hot and bothered, and more sustained warmth.
Life becomes less what they can prove and more what they can do.
They become the men they always wanted to be, and the ones women want to know. All of them seem more at home in their skin. I have a girlfriend who was ecstatic that her twenties were coming to a close. I can't say that for myself, but I can also say that there have certainly been moments . The too many cocktails.