The ChatGPT killer feature for me would be the ability to give, like on Notion or Confluence, inline comments so that the product can take those into account as a new prompt and optimize based on my input. Now, I have to place it all in the bottom chat, which is very inconvenient. I will probably work several times faster with this feature by having inline commenting (prompt based on a specific aspect of the provided answer). And as they say, in UX, confidence is king.