I’ve been on the following regimens, with comments:
1) Prozac, Klonopin, Beta-blocker (fluoxetine, clonazepam, atenolol) – this was waayyy to strong; the clonazepam hurt my ability to study and remember things. I felt really excellent, though.
2) Strattera, Buspar (atomoxetine, buspirone) – the strattera left me feeling very “cracked out”, but did marginally help with focusing and task management. Buspar helped reduce stress and anxiety, allowing me to study without worrying about things (“Am I going to finish this? Will I do OK on the test?” etc.)
3) #2+ Provigil (modafinil) – Provigil was a giant improvement in the regimen. It really helped me wake up bright and early and feel very awake and active. Also, if you take it later in the day you can work into the night without feeling sleepy. It did not affect my ability to get to sleep.
4) Provigil, Buspar, Wellbutrin (bupropion) – My current regimen, the strattera was having too many sexual side effects, so I switched to a similar NRI with antidepressant qualities, Wellbutrin. So far it has been great. Wellbutrin definitely improves your mood and also has a stimulant-like quality.

I have also taken Ambien and Lunesta to help me go to sleep, since sometimes studying at night gets my mind racing and I can’t fall asleep.

I did a HUGE amount of research into all of these drugs and am very vigilant in watching for side effects. I take my blood pressure and heart race frequently, as some of these medications can cause increased blood pressure or stroke. Communication with your doctor is crucial, since he/she has a lot of insight into whether the drugs are working, what side effects are problematic, etc.

Lastly, I think this is an important ethical issue with social implications. On the one hand, I recognize that what I’m doing is potentially dangerous, and I manage the risks very carefully to minimize this. Others could feel pressured or coerced into enhancement, which could challenge their autonomy and happiness. On the other hand, I want to do big things in the world, and don’t you want the person working on a cancer cure to be the most focused, learned, creative person he can be (regardless of natural/enhanced)?

Feel free to ask questions I’ll check back and answer them.

But then, I rarely even drink coffee or tea… I’ll eat sugary snacks though.

That 20% of scientists use something merely reveals they are human, susceptible to temptation and rationalization like any other. And being scientists, perhaps more competitive than average.