"How do people who've taken it for most of their adult life cope with adderall usage? I mean, how necessary of a drug does it seem to be -- or, to put it another way, how bad are the withdrawals, compared to antipsychotics, painkillers, etc?"
I'm 36 and I've been taking Adderall approximately since I was 32. So I've lived most of my life without it.
I've never smoked and I've never been on antidepressants or any other psychiatric drugs so I have a limited number of reference points as far as addiction/withdrawal goes. I have had an off-again, on-again caffeine addiction. In my experience, Adderall is significantly less addictive than caffeine.
Quitting Adderall is easy in my experience. I take less on the weekends, and on several occasions I've had no problems tapering my Adderall dosage down to zero over the course of 3-4 days just so I could do a little "reality check" and see for myself if I'm truly better off while taking it.
Adderall is not a medication that really lends itself to abuse in the sense that you want to cram mouthfuls of it into your body or anything.
In some ways, Adderall is very comparable to caffeine -- the first few times you take it, you feel a bit of a rush, but your body acclimates to it rather quickly and you stop feeling it. Unlike caffeine, you don't typically get the same sort of "crash" an hour later.
Though I have pretty poor impulse control at times, I've had no problem moderating Adderall usage. My psychiatrist, after a year or two of developing trust in me, actually prescribes me twice the dosage I need (30mg daily instead of 15mg daily) because he knows it will last me twice as long and therefore I can save myself some insurance co-pays for office visits. :)
I've never been on antidepressants but I've watched friends struggle with getting off of antidepressants, and I've also seen what they're like after missing a few doses. They have found themselves in really rough shape unless they carefully taper their dosages down over the course of weeks or even months. From those secondhand observations, I feel Adderall is not even close to being in that league when it comes to withdrawal.
"And if you've lived with Adderall usage, do you chronically feel like you have a reduced appetite and all the other kinds of symptoms?"
It hasn't affected my appetite much. (I kind of wish it had!) The main negative side effect is that Adderall makes me more high-strung. However, falling behind on one's obligations due to untreated ADHD can also negatively one's mood, to say the very least.
edit: grammar/spelling/formatting