Would some of the open-source alternatives fit the bill? Something like SimpleNote?
* must be a native app, not a shitty web app
* must be able to run on my Mac & iThings as well as my collaborator's Windows & Android phone
* must be able to collaborate with other people
* must be able to ingest a decade of Evernote gracefully
* that includes attached images and PDFs, I make comics
* must deal with actual rich text, markdown is nice for commenting on the internet but notes need more
I don't think Simplenote really handles file attachments, so it'd be a complete no go.
1. Be accessible an up to date 2. Easily searchable, and to do so quickly 3. In the rare case that I need to take a note, it is best if I can do so easily and have those go back to my computer quickly and painlessly so I can do what needs doing to get that into the system better.
Org-mode simply does not do this well in any of my experience with it. It's fine if all you're doing is taking notes on a computer, but as soon as you add a mobile device to the mix, it goes belly up for me.