My Cham LOVES Phoenix worms! He could easily go through a bulk amount in a week, but because they're supposedly more of a treat item, I only feed them out maybe one or two days a week. It's the only food he'll actively take from my fingers as though it was a life or death situation. The crickets never seem to wiggle in my fingers though (When I lightly hold them, of course).
So I like them in the end. They're a healthy food item and if your Cham likes them then that can be a god send for keeping nutrition stable. My only worry is that as he grows, they'll become too small for him and he'll start ignoring them.
In terms of Phoenix's as a staple, I don't think it's recommended with Phoenix worms, though I'm not sure. I try to keep my guys diet as varied as possible with crickets, dubia's, locusts, calci-worms, silkworms and mealworms with the odd waxworm as a treat. In the end I guess they're about 20-30% of his diet.