Seconding dwspivack above, I am a new user and wanted to share stacks almost immediately. While I can understand tags as a great nonlinear, nonhierarchical tool, organizing into notebooks and stacks increases the overall readability. Or put another way, if I was the only user, I'd be fine with relying mostly on tags. But I want to share notes as a training tool for my team; I'm afraid the notes might not be as readable without the file tree style organization.