I am looking for good workflows as well. So far there are too many steps and hurdles to move back and forth.
What I found is that if you select 'edit' on the screen and then 'export' and then 'plain text' and then you'll see Pages as an option.
My problem with Pages is that in this export process the line widths are brought in from the OmniOutliner instead of filling the entire screen. I've not noticed this in either ByWord or WritingTools. I've yet to try other apps, such as iAWriter.
I've noticed that when one exports an outline to another app that it will only export as text those lines that are expanded. If there are hidden lines that are not expanded they will not export to a text document. I have one document that is quite long and has many headings on it and it is a pain in the arse to go through and click every child element before exporting. I figure there must be a way to expand/close all of them with one button, but nothing works for me at this time.
As for Keynote... go from Pages to Keynote on your Mac.
Using ByWord and iAWriter, there is a sync between iPad and Mac. Once you get it to the mac it should be gravy to get it elsewhere.
I REALLY wished that OmniOutliner would incorporate better DropBox syncing. As it is I must do some workarounds and then export the document back to myself so that I can replace the dropbox item on my computer. If this were OmniFocus then all I need is syncing with each device, which OmniPlan does. However I am wanting this to be a tool for use in my workflow and as such it simply MUST be able to play well with others easily. I've started looking at other outliner programs, though I hate to do so.