I'm a senior in college. I discovered adderall my 3rd or 4th semester and have taken it about twice a year since: at the end of each semester during finals week. A couple of times I have taken it during the semester to pass a test I put off studying for until the night before. Invariably, I can retain much more information and study for much longer periods of time when I study on adderall, and practically always make A's on the tests.

I definitely go through a depression for a few days after a hardcore adderall studying binge, and probably don't retain the information as well as I would if I had studied it in a timely manner throughout the semester. I would consider this problematic if I took the drug more often, but I don't, and I still will work long and hard hours on a project I enjoy.

I thoroughly believe that attending class and doing your studying throughout the semester is the best way to go.
I also have thoroughly been bored by some of my classes. It is these classes that I skip and don't do the work for,
putting it all off until the day before test time - and learn enough of the material to get an A.