  I don't know about other guys in their 20's, but the libido causes some problems. First, the good stuff: 1. Erections are neither difficult to establish nor maintain, and frequently occur for no obvious reason at all.
2. Sex is pretty easy to get. Just go to sleep. 3. Being in shape is almost automatic as long as you eat decently and stay away from the Segway Human Transporter. The challenges: 1. Getting along with women is difficult when you're pretty much willing to have sex with anyone born with a vagina (or who has a surgically placed one. Whatever floats your boat). Consequently, conversations with women are either hard to follow because of various distractions, or it's awkward because the sexual energy is hard to temporarily turn off. 2.
High testosterone makes sleeping difficult.
3.
One of the reasons I like older women is because their drive is more on level with mine, but a lot of them have finally given up on game playing. On the other hand, getting them to take you seriously is a challenge. Or, they are attracted to you, but are not available to you because they buy into the stigma of dating someone much younger than them.
4. The majority of guys my age are still emotionally 12 years old. Gives guys with half a brain a bad name. And makes having legitimate guy friends a bit of a challenge sometimes. 5. I do enjoy the company of women in non-sexual contexts. But having your libido constantly set to warp 9 interferes constantly. Professional and platonic interactions are always at risk for becoming sexual in one way or another. 
