Well, first off Intuniv is not for hyperactivity so it wouldn't be given to kids with ADHD. It's given to kids with ADD, Attention Deficit Disorder who are lacking the hyperactivity. Intuniv doesn't have a stimulant in it, which is what ADHD often need to help them.
My daughter (who is 8 and has Autism) is taking it for ADD for a few months now and we saw an immediate improvement in her attention at school and it's continuing improvement which we can tell (since she attends summer school). We haven't had any side effects at all.
Our neurologist chose Intuniv because she's also on Lamictal SR for seizure disorder and to help with her migraines and some of her Autistic behaviors (off label use).
In our specific case I have nothing but praise for it so far. The longer she takes it the more benefits we're finding. I'm having an easier time with certain behaviors at home. She tells me that she feels better taking it. After a week or two, she said to me, "Is that what you mean when you say 'focus?' I can focus now!" She couldn't focus before so when we asked her to focus, she had no idea what we were talking about. Now that she can do it, she's amazing herself at school. She's not getting up and wandering out of class. She's not losing her temper with her school work. She's finishing more of her work. She's paying more attention in class and retaining more.
EDIT: Since there are a couple of VERY judgmental answers assuming that it's all about diet, I'm going to add that certain things in foods can trigger certain behaviors.
High fructose corn syrup, Red 40, as well as green yellow, and blue, can mimic ADHD and ADD. It's because those things are toxic to the brain and they can't be metabolized. We already disallow those things in my daughters' diets (all of my daughters) and my ADD daughter STILL HAS ADD. She STILL HAS AUTISM. We even removed dairy and discovered she's lactose intolerant. Her behaviors improved by removing all of these things because HFCS and food dyes can make these symptoms in ADHD/ADD and other neurological disorders worse. They don't just always mimic those disorders. They can make symptoms worse.
So I would say to try the Feingold Diet or a variation of it, but if you still see ADD/ADHD behaviors then you'll know that those foods were contributors to making the symptoms worse and that your child does indeed have ADD/ADHD.
Take if from a mother who knows and has done all of the research.