Also OP, I don't know if you mentioned anywhere how old your child is, but I know you mentioned that he is autistic, but did not mention the severity of his autism. I have explained to my son that Concerta is his "helper" medicine. Like anything else in life, anything in life that helps doesn't do it for you, and neither will this medicine. As far as his staying calm and remaining focused, it is important for you AND his father to stress to him that he still needs to learn how to practice self control on his own so that this medication doesn't become a crutch for him. It would also help if the 2 of you can find a way to communicate effectively especially since your child has such issues and this really can become a burden on his medical issues. Children with ADD/ADHD need structure and schedules like no other child. Therefore, it may be helpful to find out from the CP what his schedule is at home and try your best to adhere to that (bedtimes, when baths are, what happens before bed, etc.). That is not legal advice that is advice from a parent who also has a child on the same meds.
As I said earlier, doctors have no problems with Concerta and "medication vacations." It won't hurt him not to take it. In fact, like I said, I let my son go at it on the weekends so long as we don't have plans for him to go somewhere where it would be integral for him to remain focused (amusement parks, etc.). My son when he was a bit younger was very impulsive and tended to wander, so having him in some congested area without meds was a disaster sometimes. I don't have much of a problem now, because as he is becoming a preteen, I tell him that it's his responsiblility to fight the urge to do the wrong thing and do the right thing.