I am just starting out with Scrivener and have a lot of work in OmniOutliner. OmniOutliner 3.9 beta supports OOXML. It would be a great benefit to me if Scrivener supported it for both input and output. Please forgive me for my ignorance and congratulations if it already does.

OmniOutliner also supports OPML export, which Scrivener can import via drag-and-drop into the Binder.