Personal experience/medicate or not.
Well, yeah I have to agree it is a heavy decision to take into consideration, to medicate or not your child. But, you have to keep in mind that most of the conflict/controversy is over dependence, abuse, and addictive properties displayed in using these medications. Most of the media hype has been negative in publication, understandably because of it's capabilities. Speaking from personal experience using these CNS stimulants as a child, and even through college-being 26 now with an acceptable career, life, and position.
I can say that for good or ill taking these medications have strengthened my perceptions, and reactions to the down sides of this acquired disorder labeled "defect." I think they have given me a resilience to withstand, and rebound after repeated disappointments in life from all angles which is more prevalent in individuals with deficiencies. I am not talking about dependence on the drug for these attributes, but more of it gave me a sort of "crutch" or tool to learn from and ultimately inherited into my natural tendancies/personality. Yeah, I'll stick by that.
On the other hand these type of chemicals are widely abused, addictive, and have been for decades. Side effects are of concern, and I won't say I never had any negative side effects(loss of appetite, insomnia, etc.), but mild in comparison. Also the distribution of these drug have been increasing dramatic in the past 8 years, and the willingness of medical professionals to hand this stuff out is a bit of a concern. You have to keep in mind that criteria based on the diagnosis of these "deficiencies" is a bit sketchy, thus explaining the increase in diagnoses and treatment with stimulants. Their practice is to ask the individual "how effective is the drug working," and prescribe accordingly(perception). That's a bit scary too because the intentions of the patient might be different, in using it for their addiction not for their "defect." This is usually not the case in children, but performance studied by the parents/teachers are relied upon not a full spectrum of proper observation in all areas. A parent/teacher might conclude that "Yes jimmy has been so much more behaved, and his focus is so much better." In reality it may kind of create a sort of tunnel view of concentration, and may make it hard to switch activities or to enter into social interaction, show emotional personality. Initially it may actually increase confidence, and social interaction but with continual use I can attest this wearies off.
Now as far as people/science claiming it "causes permanent brain damage or damages release of the way chemicals are released in neurotransmitters in the brain, in an irreversible aspect" well even from a scientific approach I can't see how you can prove that idea. You would have to study the individual on the medication, go back in time and study him not taking the medication due to the "irreversible" factor implied. Who can say in the long run it changes the way a person might have thought in the first place?
Considering the genetics is a main factor, but also almost impossible to predict.
Sorry for the lecture, an experienced point of view