The thing is that superworms are fatty, like many larval worms, and so can be unhealthy if fed too often. But they do make a great treat a couple times a week for variety, and are easily gutloaded. I've never had any chameleons prefer superworms exclusively, but some may prefer them if they're getting bored of crickets.
The good thing about superworms is that they last months as long as you feed them, so you can order them in bulk and you'll have a back-up or treat food for months. Just remember that vareity is important with chameleons, so just incorporate superworms in to a diet that maybe includes crickets, roaches, hornworms, silkworms, grasshoppers, mantises, etc., As many insects as you can afford.