First, stimulants have a release schedule and are generally not a 24-hour thing. You wouldn't be able to sleep if they were. The effect depends on plasma concentration and varies during that interval. You might feel extremely focused at first, then energized but not especially focused, then a total drop in energy and focus when you hit the "down" part of the curve. Everyone's response is slightly different, however. I definitely think differently in the morning (after taking the pill) vs. at night. Sometimes I have an insight while relaxing in the evening that I write down and becomes my focus in the morning, when I'm better able to work.
Second, it's not easy to put into words but the focusing effect is different from the cross-topic creativity you're talking about. Amphetamine is like a really strong, long-lasting coffee without the negative side effects that would come from drinking pots of coffee at a time. Plenty of creative people drink regular portions of coffee. It lets you focus on your work without unwanted distractions. But by increasing working memory, stimulants actually increase the incidence of cross-domain insight, in my experience, because you're able to keep more concepts in mind while you're working.
I use a lot of caffeine, so if it’s comparable in terms of the “mental lane”, then I think it could put for me. The increased working memory leading to more connections sounds perfect.
Minus the jittery hands, racing heart, headache, and other issues even moderate coffee consumption causes for me.
But with the loss of appetite, constipation, and difficulty sleeping that coffee does to me too.
Definitely worth it on the balance. Being on medication is life changing, mostly for how capable it has made me in my personal life. I’m not the hot mess I used to be.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3880463/
This would be true even if the mechanism was "merely" an increase in focus. It turns out ADHD meds do more than that though, as they also improve working memory and mental stamina.