Superworms are a fine stample diet. Just make sure there approprietly sized. Are the mealworms moving a lot, or are they just sitting there? Remember gecko's hunt by movement.
They can get sick of superworms too. I have geckos who used to eat a lot of superworms, but now prefer giant mealies.
Superworms move very fast and can escape from all but the tallest bowl. So they're okay if you have time to hand feed them to your geckos one at a time, but they're not very good for leaving in the enclosure.
My main problem with superworms is that the substrate they're in burns my throat and eyes really, really bad. I've had some just sitting here for a while since I've been feeding more mealies and crickets lately. Every time I sift the superworms to put them in new bedding, I wear a paint respirator and mask. I think I'm just gonna get rid of them.
One of the aptors I hatched last year may have gotten an upset stomach from eating too many or too large of a superworm as well. At one point he wouldn't eat for a while. Luckily, he's now eating a few giant mealies or crickets, but he doesn't eat a lot at one time like he used to. So do be careful if you're feeding supers. Don't feed small geckos large ones for sure.
There was an article about leopard geckos in Reptiles magazine a few months ago. The author said that leos should mainly be fed crickets, supplemented by some worms. I know some breeders feed exclusively mealworms with no problems, but I still think crickets are the best. I feed crickets and mealies/giant mealies, and I just tried waxworms the other day. Most of the geckos I gave waxworms to liked them, though a few didn't.
I had been feeding my gecko superworms the past week and a bit or so, and he has only actually eaten maybe 6 or 7, and I think he is deciding the other ones are too big. The biggest problem though, is the first one he ate he puked up later.. He was fine for awhile, but then last night I fed him 3 more (this is about a week later after eating other things with no problem), he puked up 2 of them at night... So I am not going to use these worms anymore. Only maybe 3 or 4 of the ones he has eaten have gone through without issue.
Thats the last time I listen to the reptile shop owner when I think otherwise.. She convinced me not to get mealworms because they were too small. I think she is retarded.
Ive never had a problem feeding superworms i switch back and forth between supers and mealies tho, almost through the 1000 supers so i jus put in an order for 5000 mealies and ill probly do supers again after that.