The reason why I was productive in college and pulled 4.0s most semesters is because I actually found my coursework interesting. It wasn't something I was plowing through because the degree would get me fame and fortune. I didn't need exogenous motivation in the form of a pill.
I know three people who swear by Adderall/Ritalin/Vyvanse/etc and I've heard the same summary from each of them: "It helps you get through boring work, but it kills your creativity." One guy will switch between pot and Adderall to do his work. He smokes when he needs to be creative and takes Adderall when he wants to bang out lines of boilerplate code.
The substance lifestyle really isn't something I can buy into.