I am one of those who had to buy their own first car. It didn't even have a radio (or a transmission) but if someone bought a car for me, I would jump at the chance to upgrade and whatnot. If they bought it for him, he should be allowed to do what he pleases. It is his opportunity to show that he can take care of things, maintain them, mold them to his liking, etc. I might not like it if my kid wanted a ricer than sounded like my lawn mower, but I would give him a chance to be responsible with it. There is more to being a responsible car owner than just paying the bills for it. I think many of you have lost sight of the other issue that come with car ownership. I see him having a head start in that he begins with a reliable car, but if he is mature enough (I have seen any blatenly comments to prove he is less mature than the majority of people his age) to handle the responsibility.
As for those who gave money to their parents, mine would disown me. They would rather starve in the streets than take money from thier kids. You can show your appreciation in other ways by keeping your room and restroom neat and orderly or offering to pay for dinner sometimes (when you want to go to a specific place) But paying them back for the car may be futile if your parents don't need the money and you can put in a better place (college, home, [not car audio], etc)
I have been hungry so much of my life, I would be a glutton if I ever got the opportunity.