HELL YES (assuming I retain everything I've learned). I've actually thought of this plenty before, and I would go back to being about 7. I'd stay away from martial arts and chiropractors and not be a god damn cripple today.

I'd get my schoolwork out of the way with ease, then spend my spare time studying biology and medicine, and by the time I'm 18 enter medschool with at least half the knowledge already learned. I'd be labeled a genius because of obvious mental superiority to my peers, and probably be a neurologist or go into some type of research.

That, and I'd go through junior high agian where I was bullied ruthlessly into a horrible depression and near suicide. Instead this time I'd have the confidence and experience to kick some serious friggin ass and make a strong social group. I would definately do all the physical and mental training I do now from a young age.

and maybe.... just maybe..... I'd predict a whole bunch of future events. Then when they come true I'd tell them I'm psychic, but only know certain things about the future, and that they must not vote in George Bush or the world will crumble before us. (well realistically I probably wouldn't mess with the order of the world so much, but it's tempting).