My problem with it is that I've personally seen really only bad results, not good. Honestly, I've never personally met a child "before" and "after" ADHD meds who needed it. I've only seen adults who were on it as children and ended up with problems and then people who abused it... I have zero experience with small kids on it. And of course, when for example my child has strep throat I give them antibiotics. I'm just opposed to medications that can be sidestepped with natural methods (i.e., sleeping pills). By all means, if a child's life drastically improves with medication they should take the medication.
The effectiveness of these medication may in fact be the reason you don't know about any "before and after" children. The biggest problem with the meds if finding the right one for each child, and the right dosage. I thankfully did not end up medicating my DD, but did have to seriously consider it - and the ONLY reason we didn't end up medicating was because of an exceptionally supportive school environment. Even so, I suspect if we chose medication, DD would be and even better student, but we have chosen to avoid them.
It's not just that ADHD is overdiagnosed, but that it is underdiagnosed at the same time - many who don't really have it are diagnosed, and because of the stigma associated with the diagnosis, many children who should be diagnosed are not.
Those adults you know who abuse these drugs are no different than those who abuse other drugs. I know many adults who are irresponsible, and probably should lose custody of their children, and it almost always boils down to selfishness. Those who abuse prescription medications like the way they feel on them, and choose that feeling over everything else - no different than the alcoholic who chooses to drink, or those addicted to more "traditional" drugs. In my experience, for those the drugs work on, they either don't notice the difference themselves, or don't want to take them - they're the ones that say "I don't need them anymore, because I've been cured." Well, yeah you're acting better, but that's BECAUSE of the drugs.
There are many maintenance drugs, used for a variety of reasons. When needed, they do wonderful things, but there is always the potential for abuse.
As for those college students, the drugs (even no-doze) don't really help long-term. Cramming will allow you to retain the information for a test the next day, but most of it won't make it to long-term memory. When you take your next exam, you have that much more to memorize. I recall many professors who preferred open-book tests because more difficult questions could be asked.
The M&M parties do scare me, and they are not just college student, high school students hold them too. Young adults, and those approaching adulthood don't have the best judgement, and some adults never learn it either. I my college days it was alcohol, though I recall a few classmated ending up in alcohol induced comas, and two who died of alcohol poisoning, so maybe it's not really all that different.