As someone with diagnosed ADHD, and prescribed something similar:

It's not that they make you superhuman - I don't think I'm any "smarter" on them. It's just that without them, my "productive" bursts would be at really random times (11PM or 2AM), and make it very hard to fit into a "normal" schedule with the rest of society (I would frequently fall asleep in classes or meetings).

So it's more that it allows you to "rearrange" the same (or slightly larger) amount of work but into a more reasonable, traditional schedule. And for certain things, helps more than that. But it's not a miracle drug by any means.