I cycled modafinil/adrafinil and caffeine. For me it was a much stronger focus effect than caffeine and a much weaker effect than amphetamine. However, I developed an intense case of the hives after use which occasionally (1/2y) recurs without use with no prior history. This is not an uncommon side effect according to the doctor who I reported this to.

In my case I experienced no physical dependency on any of the drugs and chose to stop because I wanted to perform other experiments. I’d say it’s about half a decade now since.

I do know others who get weakened impulse control but I just get hyper focus of various degrees.