I took ritalin one time as a teenager, cause my friend had some; the three of us who were hanging out each took one.
I can still vividly remember that entire evening. I had the most clear, focused mind I've ever experienced in my life. Felt like I could have learned any subject with ease, felt like I could have solved any calculation or puzzle in a snap. We sat there having one of the deepest conversations I'd ever experienced in my youth, and then hours later we went to a beach in the middle of the night and swam out and climbed on some rocks. Easily could have drowned, but we had the time of our lives.
For me, ritalin had a HUGE effect, although admittedly it was just the one time, not a regular thing, so it can definitely make a difference for someone with a brain like the one I have (poor saps

).