I think that getting a specialist to work with you might be a good idea.
For example, you said that your son did fine on V and then things changed.
I would have asked you, at what time did things change? Was he fine at school for a period of time? or impulsive from the start? If he was fine for awhile, it would indicate that he just needed a slightly bigger dose of V.
Also, a high protein breakfast makes V much more effective - http://www.corepsych.com/2008/11/add-adhd-medication-find-the-sides-of-the-therapeutic-window/
While it is true that all the stim meds are somewhat different and thus effect people differently. And it does take some trial an error to find the right one - I am a bit surprised that she gave up on V so quickly. And more surprised that she went to the intuniv, with out trying some other things first.
Oh, the other thought is that things like a good nights sleep can really effect the day. Did the start of school throw off his schedule?
Even though he has only been on Intuniv for two weeks, I am concerned that all documentation says to taper off of it - not suddenly stop it.
Anyway, It seems like there are a number of questions that your GP should have asked before adding or switching meds. That is not a good sign.
And yes, Concerta is a good med. I don't know about the price. Kind of think that if you do start it, you should start at a lower dose (personal opinion).
By the way, I always recommend the book, "The ADD/ ADHD Answer book," by Susan Ashley (about 10 bucks on amazon.) You will find it very helpful. I hope some of this was helpful. Please post if you have any more questions. Best wishes.