Though OmniPresence provides similar syncing as services such as Dropbox or Box, Omni Group says that it is more compatible with OS X's Versions and Auto Save, and that it better handles file structures such as OS X's package files. I found OmniPresence worked exactly as claimed, synchronizing items effortlessly between devices.
After you have created and styled the perfect outline, you might want to export it for use in other documents, such as a Word or Pages file — in fact, Microsoft Word export is one of the Pro features. However, I found it to not work very well. Plain-text outlines exported fairly well (though outlines exported to Word are limited to only the left-most column), but if you spent lots of time fancying up your outlines with OmniOutliner's styling tools, those styles will not export well to Word. Some outlines ended up in Word with unacceptable background colors, and I even had styled text appear in Word as invisible white text.
RTF export is little better; though Word is a common target for RTF files, OmniOutliner's RTF files showed styled text with better fidelity in TextEdit than in Word.
Though an outline is a perfect way to create the structure for a presentation, OmniOutliner's Keynote export creates a file in a version older than the superseded iWork '09 format, not to mention the current Keynote 6 format.
Pro and Standard
You can purchase OmniOutliner 4 from the Mac App Store or from The Omni Group. I suggest you try before you buy, and download a 14-day trial from the company's Web site. During the trial, there's a handy toggle in the OmniOutliner menu that allows you to set the program to Standard or Pro mode, so you can get a good trial of just the version you are interested in.
The Pro version costs $50 more than the Standard version, and provides several additional features, including expanded styling options, more control over indentation and line heights, the ability to hide and show columns, AppleScript support, manual page breaks, create customized toolbars for particular documents, and different ways to customize and display notes. Many of these features you can live without, and I'd suggest that you audition both versions before you spring for the Pro features, because you can upgrade to Pro after purchasing Standard.
OmniOutliner 4 requires OS X 10.9 Mavericks, so if you haven't upgraded to the latest version of the OS, you can't run it. If you purchase the 4.x program from the Mac App Store and aren't yet running Mavericks, you'll be offered the 3.x version, and once you upgrade the OS, you may then upgrade OmniOutliner at no further charge. The Omni Group says that Mavericks is required because the user interface upgrades they implemented in OmniOutliner didn't work well in Mountain Lion, and since Mavericks is a free upgrade that runs on almost the same hardware as Mountain Lion, they chose to exclusively support the current OS.
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