Besides the obvious monetary stuff, I'd be going into my second year of university knowing that I am autistic and having learned a lot of the social skills and coping strategies that I learned from therapy. I'd probably be able to find a fulfilling relationship before I turned 20 (rather than 28), and I would have felt far more comfortable joining up with clubs and groups at school and developing a social network.
I often feel bad that I only started getting help with those aspects of myself within the last couple of years. But I wasn't aware that I was autistic.