Our experience was similar to crazymomma - although my son was successful on adderall for a number of years, he also had increased aggitation as a side effect - but the overall benefits outweighed that side effect. Then, in 7th grade (about 18 months ago), he began to struggle with additional focus issues in the classroom and 5 more mg's were added (xr). We began to see some increased aggitation and frustration in the afternoon so we went back to discuss this with the psychiatrist. The psychiatrist said that difficult child was probably hitting the afternoon punch of the adderall. He suggested vyvanse and said that most of the teenage boys that he rx'd did well on the vyvanse and said it made them "feel more like themselves".
While adderall and vyvanse are similar, the vyvanse is different in a couple ways. As compared to the adderall XR, it does last a few hours longer and suppresses the appetite more. Additionally, it has a smoother release system than the adderall and does not do the morning and afternoon "punch" of medication like the adderall. We went with the vyvanse and it has been a great fit for the last 18 months. The vyvanse does not seem to have the increased aggitation side effect like the adderall had - he seems "smoother" on the vyvanse. difficult child takes 30 mg every school day - never on the weekends, school breaks or summer.
I hope it works as well for your son, but remember, all kids are different. My son has been on four adhd medications over the last 8.5 years. As things within them change, they grow, go through puberty, etc., their reaction to medications change as well.
Sharon