A lot to be said about the cliche that age is nothing but a number. Although, looking old enough (or young enough) to get carded thanks to exceptional Asian genes is a huge plus.
What's it like? It really depends on where you are in life. If you are mature (i.e.- spouse, kids, got really far in your previous career) it's going to be tough, and sometimes you'll feel almost paternalistic (maternalisitic for female?) and you end up being like a groovy camp counselor, where the only time you get much extracurricular interactions w/ your classmates is when they want sage advice - about life, relationships, finances. But it really won't be anything more than as superficial as that for the most part.
HOWEVER, since age is nothing but a number, and I went into med school (at age 33) no wife, no kids, and usually binge-drinking/partying on the weekends, I fit right in. If you imagine YOURSELF when you graduated from college, doing the living life/carpe diem/YOLO stuff, then you should have no worries. Cuz that's the extracurricular activities that almost all of your classmates will be doing given any sliver of recreational time.
This aspect will dictate how well you get along w/ your pending classmates. If you are the former, you will end up developing a mostly "working" relationship with them. If you are the latter, like me, you will make friends quite easily. Which you can take one step further, say you are single, and need to date. Dating, in med school is like fish in a barrel LOL Once you are "cool" you can date pretty much anyone. The microcosm of the med school "ecosystem" is a strange thing. Yet, the folks you date will probably be way younger than you are.
To go one step even further, this will be the same way when you get into residency, though it depends on the demographics of your program. You will either make friends w/ the people in similar situations. Because we have mostly the "mature people" clique, and the "single people" clique. The latter going out and partying most weekends.