Based on OmniGroup comments posted to MacUpdate, it's clear that this release of OmniOutliner is a deliberate decision to deliver much of the writing/outlining functionality of MORE 3.1. (OmniGraffle would be a variant of the graphical portions of MORE.)
They've even implemented a variant of MORE styles. This help file entry tells a veteran that this is a very well designed Mac application:
By default, when you attach a file to an outline it gets embedded into the outline. This means that a copy of the attached file is actually put inside the outline file itself. If you subsequently move the file around, or send it to someone else, the attached file will move with it.You have to love a vendor who writes documentation like this.
If you attach a folder, or hold the control key while dropping a file, an alias to the file or folder will be created instead. The alias behaves just like an alias in Finder, as a pointer to the actual file. This means you can change the file or move it around, and OmniOutliner will try to follow the changes. Of course, if the file is deleted, gets moved to a network drive that is then disconnected, or otherwise goes where OmniOutliner can't find it, the file reference in the outline will become useless. Also, if you want to send the outline to someone else and have the file references stay valid, you'll need to put them all into the same directory structure and send them the whole mess.
This product is a cross between a database/spreadsheet, a wordprocessor, and an outliner. Given my history w/ MORE I'd be dishonest if I didn't buy it. So I have. (List price is $70, I paid $40 for the academic upgrade price.)
This looks to be my primary writing tool for OS X. I'd expect that if Apple announces an iWorks wordprocessor, and if the Apple file format is not completely impenetrable, that OmniGroup will support that file format. It does support RTF import/export so Nisus is another possible complement.
I'll update with more experience. If it works well I'll look at OmniGraffle integration too.