I feel like asking it to polish or rewrite is going too far. Using it for a grammar/spell checker or thesaurus is fine, though. At least that preserves ones voice.

And I've definitely used it when I can't remember that one stinking word that I know exists and is perfect for this occasion.

> one stinking word

"hey robot give me every word even mildly related to $SOME_SENSE_ON_THE_TIP_OF_MY_TOUNGE" is a wildly satisfying and underrated experience.