The Drag and drop is a bit muddled when creating sub documents. I like the drop down option of "Add Page Inside" - very useful.
But a bit of a snappier or more obvious interface would be helpful to know exactly where I'm moving the Document to.
Right now - hovering over the target document to sub-doc under will actually remove the document from that 'folder' and up-level, instead of subbing it. I'd intuitively assume that when I hover over and it turns darker, the document would sub under the target darker doc.
Hope this is clear enough...