OmniOutliner is great; I used it to put together the panel remarks I mentioned an earlier breadcrumbs item.
The XHTML export support is quite good, and even their native format is XML. But it's a bit of a pain to remember to export each time I save so that I can keep the ooutline version and the XHTML version in sync.
Why not just use an XHTML dialect like XOXO as the native format? I wonder what, if anything, their native format records that XOXO doesn't cover and couldn't be squeezed into XHTML's spare bandwidth somewhere.
There's also the question of whether XOXO can express anything that OmniOutliner can't handle, I suppose.
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