[russcus]

I have been experiencing this unwanted behavior with Mountain Lion 10.8. OmniOutliner always opens a new untitled document when launched regardless of how it is launched (directly or by opening a document) or its state when last quit (windows open or not).
Deleting the preference file, as suggested in this thread, did not resolve the issue.
I went into System Preferences / General and cleared the check box for "Close windows when quitting an application" Refer to the attached image. The notation for the check box says "When selected, open documents and windows will not be restored when you re-open an application." While this is confusing and non-intuitive, it does resolve the OO3 behavior issue