I personally know a top college distance runner who takes ritalin/concerta for same reasons (has ADD). Has been taking this med since soph in HS. Meds had no effect on running, neither positive nor negative. But when this person stopped taking this med 5 days before a USATF competition (so it would clear body and not result in positive drug test), about half the time this runner has a bad race.
Runner now has a TUE from USADA so there is no longer a need to stop the meds before a USATF race. Getting a TUE for Concerta is quite difficult but possible if your doctor can convince USADA you have rather severe ADD. By the way, USADA/USATF have no problem with, and in fact encourage runners needing to take Concerta/Ritalin to stop taking it (if they can) 5-6 days before a USATF competition where they could be drug tested.
Only other side effect with this meds is it will decrease your appetite during the day, but as medication wears off during evening hours you might get quite hungry. So it will take a little effort to eat properly. That's it.
Don't take advice here from anyone who hasn't used this medication. You get a lot of people with a strong opinion on this that clearly have no idea what they are talking about. Also one's experiences with Concerta can vary somewhat or even a lot from person to person. You are going to have to try this med and see for yourself what side effects it has on you. If you have moderate or worse ADD, taking Concerta will NOT be a performance booster for you.