There was a Mad Science class at our local GT enrichment classes. It was a popular class, and DS7 (then 6yo) enjoyed it. It was in the top three classes of the 6 he took. I think he ranked it second, behind engineering, which people fight to get into every year. No class can beat engineering! So 2nd place is high praise.
I will say that he was one of the younger kids in a class of all GT kids (though of varying LOGs), so the placement was probably pretty decent. Also, I don't know if she scaled the material up at all for the GT kids. She may have.
It seemed heavy on science and experiments to me. They did nothing I would call a craft. They made slime, built a "car" powered by a twisted rubber band, looked at bugs. Stuff like that.
FWIW...