i've never raken ritalin or adderall, but my experience with them is seeing how friends have reacted to them. i've been close with a bunch of people who, in order to get work done, had to be on them. their add/adhd was strong enough that it was such a trial for them to focus without it, so they'd pop one and settle down to do some work.
but it's not a stimulant in a fun way - they actually became kind of externally numb, they were so internally focused.
looking back, it's not something that i would want to try in combination with bike racing.