I didn't have my son do it last year in 7th grade (would have been ACT or SAT) for Duke. I felt like he has too much anxiety and it would piss him off to see the math stuff he hasn't been taught. If he could have done all sections but the math I would have had him do it (he has Asperger's and I didn't want to spend years undoing a potentially horrible experience and have him wreck his chances of being successful later when he did have the proper math instruction behind him). He is a logical mathematical thinker and looks at a lot of life through a mathematician's eyes but the reality is if you haven't taught him, he doesn't know how to do it. But he picks it up quickly.
I probably will do talent search with my younger son. But he doesn't have the challenges that come with Asperger's and has tons of confidence and not much perfectionism (he is perfectly fine with making a mistake and moving on). He is in third grade so I haven't figured out much about the talent search yet.
My mother though said there is some sort of special summer program at the Naval Academy and she wants to find out more about it and send him to it. It is special things like that that I would want him to qualify for (but we might not have the funds to actually send him, so my mother offering to pay was very sweet and thoughtful).