Just like anything else, moderation is key. Someone with an addictive personality or substance abuse issues might want to steer clear, but I'm also the guy who has bought just a single pack of cigarettes a month for 6 years.. I'll have a few on the weekends when I go out because I tend to enjoy them when drinking/socializing, but never crave or smoke them casually or by myself.
Anyway, I'm prescribed 40mg a day (two 20mg instant release) but only take them 3 - 4 days a week when I'm planning to get some serious work done. Even then, I crack the 20mg instant releases in half and take the 10mg halves gradually. I prefer to space them out like that and I almost never actually get to the fourth one.
Despite how much I enjoy the concentration, energy, confidence etc. that comes with adderall, I never take large amounts (never more than 30mg at once in 2+ years) and take a month break or so every 3 - 4 months. I see plenty of people who start taking more than they're prescribed to chase that good "high" though and it ends up being a problem for them.
It's a great tool to have if you use it responsibly. Just don't end up relying on it and you'll be fine.