My son was on Rispirdal for two and a half years, we just switched to Abilify this past summer.
It worked very well for him in that you could definitely tell when it was time for a new dose/he'd skipped a dose. It minimized meltdowns considerably while he was on it. Same side effect as the others mentioned-he gained about 15 pounds over the course of treatment with it.
Along with the others, if a doctor has a valid reason for prescribing it, I'd give it a try. Put it this way, if your son was diabetic and had been prescribed insulin, would you deny him medication. I'd suggest you fill the first script and see how it goes. Question your son on how he feels on the medication. My 10yo DS has always been quite honest with how he feels a medication is helping (or not helping) him.
I will admit that at first, it concerned me that it is used for bipolar and we're thinking that he is. However, it's used for several issues successfully. It worked well, but Abilify is a better option for us. Like Forevryoung mentioned, it's trial and error with medications. For instance, all the stimulant based ADHD meds would overstimulate my son.
Anne, funny that your DS sleeps like a rock on it-Neil didn't. We eventually added Clonidine to get him to sleep (which works about 65% of the time).
Please, for the sake of your son, try the medication. If it doesnt' work well for him, at least you gave it a try.
BTW, there's only one med that my son is still taking since his diagnosis of Aspergers and OCD 5 years ago. You learn to roll with it. At least now, it's only 4 meds and he takes them on his own most of the time.
Suzanne