... now exists in the form of Outlinely. I'm sure somebody's already mentioned it, but it is, in fact, a perfect duplicate of Workflowy - as a desktop app.

Any Mac users interested in saving out Workflowy files offline might wish to take a look. It's nice!

Just been playing with exporting OPML from Workflowy into Outlinely on the Mac (yes, I know, don't I have anything better to do?!), and it works quite nicely, although HTML codes embedded in the notes to individual items aren't 'translated' properly. Odd, because rich-text formatting in the actual items appears as it should.

Maybe of interest to Workflowy-lovers. I have to say, the web app works nicely on Mac, however! Although it appears to confuse the program switcher slightly, if you happen to have your main browser open at the same time. It seems to confuse Google offline apps with Google Chrome (my preferred browser - I've tried to love Safari, but Chrome's like, well, coming home).

Workflowy exports pretty nicely to Tree too, which is also a very nice Mac outlining app.
(the big novelty of Tree is the horizontal layout, but there is also a standard vertical layout as well.)