I have tried using Workflowy for some of my PRDs. I love its search-by-tag capability in which they’d show all the points related to the tag and hide others. For example, I often search for ‘#need-content’ and it quickly displays all items to which I still need to supply more content; all other lines, which have no #need-content tag, are filtered out.
One thing that I wish they’d support is an option to use numbered lists (point #2 in the post), instead of just bullets. I’d assume we could utilize its ‘Add Note’ feature to start a discussion around a particular point.