Single function text prediction, class boilerplate, some refactoring.

It's decent when you inherit outrageously bad legacy code and you want better comments and variable names than "A, x, i", etc.

You do have to do it within an editor that highlights all changes so you can carefully review, though.

Not so much a productivity boost, but rather a bad intern you can delegate boring, easy tasks to. I'd rather review that kind of code than write it, but of you're the other way around, it's a punishment.