Took dexamphetamine, but didn't take caffeine. Caffeine can be a big help at times, but it loses it's effectiveness and I get bad side-effects after a few weeks of taking it, including physical and mental fatigue, angular cheilitis, an unpleasant sensation in my head which I think is caused by vasoconstriction in my frontal lobes, dry mucus membranes, a loss of creativity and initiative, irritability and difficulty in making decisions.
The side-effects from dexamphetamine are very few and mild compared to caffeine. The only area in which it's worse than caffeine is the withdrawal when I take a break from it. When I take a break from caffeine, I can feel shitty for a few days but I'm usually still reasonably functional, but taking a break from dexamphetamine usually entails sleeping for 18 hours a day for the first few days and being very unproductive during my waking hours. It's not as unpleasant as caffeine withdrawal can be, and it can be quite relaxing at times, but it's frustrating to have a week in which almost nothing useful gets done.