I've used a sample, years ago - once - just to see what it did.

It seemed to me to be pulverized crisco covered in flour or something. It worked fine. I just didn't see an advantage and it's probably still part of my shore-lunch bag.

I don't use much oil/grease and prefer to add fake butter near the end of the cooking stage. And no, I have no idea why I don't use real butter beyond the squeeze bottle being easier to transport.