DD was tested at 7. At the time she was really falling apart: stressed, exploding every afternoon, convinced that she was stupid, that school made no sense because she wasn't smart (when in fact is made no sense because it was slow for her). She knew, painfully, that she was different, but not how... so she determined that it was because there was something wrong with her.
There was no question but that we would tell her the results of her testing. We did it for her sake, to help her understand herself. Yes, we had to guide her thinking about her intelligence. We talked over time about how kindness is more important than smartness, how she still has make the effort to learn even if she can learn faster and farther, that she should be proud of her accomplishments but there's no accomplishment in an IQ score, and that what she does with her intelligence is what's important. To us it was the same as if we had a child who was struggling because of a LD... it would be cruel not to explain what was going on with them, to help them understand.
However, if your DS is well adjusted and generally happy, I don't know if there's a benefit to him to tell him. In that case, maybe a more general answer (you're lucky to be very bright and there shouldn't be anything you can't learn about with a bit of effort) is the way to go.
