I enlisted in the USAF at 17, and spent 8 years active duty. Regrets, heck no, I served under Ronaldus Magnus!
As for advice to young folks, I'd say do it. My service made me grow up and think about what I wanted to do in life. Going to college at 26, I was light years ahead of my classmates, except one. He and I were both USAF vets, and vied for top GPA every semester.
signed my DEP enlistment with the Corps when I was 17... the OSO got hold of my ACTs, (30 composite) and offered me a full ride NROTC scholarship... I'd given up hope ever goin' to college (we were too poor) and had never considered being an Officer, but I took the scholarship and never looked back...
my only regret is getting broke and being medically retired at the 15 year mark... wish I were still with my brothers...