i took concerta for short time. it did increase my memory and i studied more efficiently. but my friends and my wife all thought that i was a jerk when i was on the stuff, so i stopped. now i have resolved to learn things in a way that works for me and trust that i can do well if i just put in the effort, even it it means studying more than others.
as for how ritalin made me feel: very goal oriented, easily frustrated if things didn't work out the way i thought they should/would, high strung, able to focus very well, but sometimes with a closed mind.
now i am open minded, creative, and i just have to study a lot to beat things into my head.