M.J.
Our son has been on Concerta about five years now. At first, you'll likely see a decline in appetite. It can be shocking, but stick with it. It gets better over time. Also, you can feed your child a lot in the mornings and evenings, when the medication isn't active.
We haven't seen any other side effects from Concerta. It's been by far the best match for our son. I love Concerta! It's given our son a normal life.
My best advice, though, is that if you don't like anything about the medication once you start it, realize you don't have to stick with it. I call our son's psychiatric nurse all the time with questions and we stay in touch with his psychiatrist about how things are going. Be the same way. If you aren't sure if something is normal, call. If you're not happy with Concerta, stop it.
Good luck! I hope Concerta proves to be a good match for your son, too.