Speed certainly helps everyone become more productive ADHD or not, but it doesn't actually make you smarter (at least in my exp). Also the side-effects of regular use were too severe for me to keep taking it.

But damn the first time in college I took a 20mg and it was like a whole new world opened up for me: I felt super-human and the amount of work I was able to churn out was incredible. But like all things, it eventually catches up to you and you turn into a cracked out zombie whos muscles hurt and can't sleep.