Well. Everyone needs different things. However my point was very serious: collaborative editing is not a special feature any longer. It is just expected in such a toll. And expected in high quality, for that matter.
Now. Evernote offers a form of collaborative editing since many years, albeit in a terrible quality. Think how even simple sync issues (even from one user) are handled.
and also part of the game: versioning. Also existing, but in an obvious screwed on way and also in very bad quality — in every regard from UI to clients
I am quite certain you don’t sell such a product anymore in a few years if this is not just working well. Again. Check out the examples I mentioned.