One of my housemates in undergrad would buy it batches and deal it to people. I never tried it myself though. He said it just allowed him to be more focussed on what he was doing, without getting distracted. Though he also said that this had a downside. If he did become engaged with something unproductive it would be much harder to then start working again. It sounded a bit like a tunnel-vision of concentration. A bit of a double-edge sword in that way. In terms of any health effects, the only thing that would crop up were headaches I think. Though one of my friends who took it irresponsibly ended up puking blood. Obviously I can't say for 100% that correlation equals causation here. But that's what happened. At the end of the year said housemate got the grades he desired. Though I'm sure he could've got them without the drug if he really wanted to.