First ChatGPT answer (AFAICT) was posted yesterday, and I didn't notice.
There's debate, and while I'm inclined to favor a ban, I won't argue.
Main problem to my mind is that ChatGPT is good at posting nonsense that looks valid. It's also true that DSP.SE users don't have the energy to point out every false or misleading claim, even (as is often) with human users.
Since such answers are due lot more de-facto skepticism, I think there should be policy requiring ChatGPT answers be labeled as being by ChatGPT. And answers we suspect are ChatGPT but aren't labeled, should be flagged.