I went off medication when I was 18 and struggled for a long time before going back on medication a few months ago. I'm 26. I did learn a lot about how to manage it on my own as far as time management goes but in general I'm definitely better off medicated. The difference in my life since going back on it has been significant. It's definitely not for everyone though. I'm on a pretty low dosage of Concerta (18mg a day) and it's unbelievable how much it has helped me, I wish I had taken the plunge sooner.
I was on Concerta for a week or two in middle school, but unfortunately my guardians decided it was too expensive/not effective even though I'm pretty sure it wasn't long enough to establish the latter.