Amphetamine is a valid drug for treating ADHD and lots of other diseases. It works and because of that it has side effects. Generally speaking if there are no side effects, there are no effects. Some of these side effects can be seen as pleasant by some people so they abuse it. There's nothing wrong with the drug but with the people abusing it.
I couldn't disagree more, there is absolutely something wrong with the drug itself. Adderall (or a light meth as you put it) was banned many years ago in Canada and presently it's classified as a class 1 substance, putting it right up there with cocaine and heroin. Basically it's poison like all the rest, people just can't differentiate between what some thug on the street is selling and what the "nice" drug dealer (pharma) on wall street is selling the public legally in certain countries.
The problem is knowledge or lack there of. There is no difference other than one dealer having a license to ruin people's lives.