1) It's given me confidence I never had before (though I'm still pretty lacking). I think being trans teaches you courage, because you sure as hell need it.
2) Also, as rmaddy said, knocking a few privilege points off for those of us who are white AMAB able-bodied etc...
3) Being trans is beautiful.
4) Most people just feel okay, or less than, about who they are. Since we have to work so hard to become ourselves, we appreciate it more. I imagine it will be a sort of lifelong serene elation after I've transitioned.
5) It's a hell of an education. Most people are just caricatures of their birth gender (the way they sit, walk, talk etc.) and know nothing about the others. Sure, cis people CAN learn the stuff that we learn, but they almost never do.
6) I liked the point about being in control of our hormone levels!
7) (For trans women) You get to cheese off insecure misogynists by being a woman who's taller than them.

The community! Having a tribe! I'm only juuuust starting to get involved in the trans community, but it seems great.
9) In the future, if I manage to feminise my voice, I'll have a "party trick" of being able to do a guy voice/male impressions.
10) "Both sides now"/"Once a man, like the sea I raged" - you see life from both sides, which is a rare experience.
I'm sure there's more.