Autocorrect is a bad idea. The kind of spelling error that iOS corrects (At least as far as I know.) is a syntactic error. Whereas the kind of error that autocorrect introduces is a semantic error. A semantic error is much worse than a syntactic one. At worst, a syntactic error leaves your meaning ambiguous. At worst, a semantic error leaves your meaning incorrect or inverted.

Usually you can read past a syntactic error, but a semantic error could change the tone or meaning of your entire message.