I used small amounts of dexamphetamine during my university degree.
I got them from a friend who was prescribed them for his ADHD. I typically used half his prescribed dose, 1 5mg pill daily when I felt it was needed, a very mild dose. I found the effect very similar to a standard dose of caffeine, but less harsh and volatile than caffeine, caffeine felt very 'rushy' a strong high, and the comedown from caffeine was harsh, amphetamines felt comparatively much milder and less unpleasant than caffeine (I have no caffeine tolerance).
It helped my ability to concentrate and study immensely. I have always had a lot of difficulty overcoming procrastination, distraction, and concentrating on work.
It has nothing to do with lack of sleep or avoiding sleep. After taking them a few times, I made a rule never to take them after 11am, they enabled me to do work in the middle of the day when I would struggle to otherwise, and I always got 8+ hours sleep at night. I had to do all-nighters occassionally for assignments of-course, but I never took amphetamines on those occasions, I find it a lot easier to concentrate naturally after 11pm for some reason.
There's nothing unethical about it, you still have to do the work and learn the information.
I haven't used them for several years now, and have suffered no adverse effects.