When it's used as a tool where the user understands what it is, it can be powerful. "How could I rephrase this paragraph?", "What API library might be used to reverse the flange polarity?" or "Can you find what seems wrong in this data?" are uses that are valid because *you* as a user can validate the output. You don't know the answer, but know what the right one would look like. "Is this mushroom edible?" is not, because the verification step would also be external.