Sunny My own experience, and you are fine to choose to ignore it if you want, it is only offered with good intention, was that a diagnosis for DN, which my DSil had to fight very hard for at about the same age as your DS has only been a good thing. No funding has ever been allocated, I guess you would call his HFA 'mild' or 'on the cusp' too.
It allowed a more sensitive approach by the primary school in all aspect of school life. It also allowed him access to a highly over subscribed high school that was far better suited to his needs which he would never ever have received a place at with no diagnosis. That's massive in itself if you consider that one fact.
I also allowed them to access training for themselves and and whole range of extra curricular resources for DS not available without a diagnosis. Being surrounded by kids like himself was a massive confidence changer for him. It's very clear now that my DB has the condition and strangely, that has helped them as a family too.
In terms of a diagnosis holding him back, well DN has just started his first term at Durham and passed 5 A Levels, 3A*'s and 2A's. So if you count achievement in those terms, then he's a success.
If you count success in how DN handles social situations, reacts to others and generally functions in society and is happy, then the diagnosis has been massively successful too.
I HATE saying this contrite term, but you would hardly notice.