This is a great outliner. I'm quite impressed by how fluid it is. Great work! quick question: why you chose to go with HTML instead of making OPML the default file format? I'm not judging, I'm just curious.
I want more structure in the file format. OPML is perfect for plain text outliners. But if you want to support rich text then you need to encode the HTML as plain text. This means it's all of the sudden harder to process with web tools like xpath. Also (not sure this will happen, but I plan to try) I expect to add different node types. For example right now every node is a paragraph. In future might have ... A HEADIN…
Anyway, congratulations on the impressive first public release. The more outliners the better in my opinion.