This is an excellent plugin! I tried several similar plugins, and most of them didn't even work; I found only one other plugin which did work, but I didn't like its interface. What I like best about your plugin is that there are no new admin menus -- it works right in the Pages screen and provide the drag-and-drop functionality that I've always felt belonged in WordPress in the first place! Thank you so much for that.
I watched your demo video, and I agree that it's not hard to use Quick Edit to change the parent of a page. That being said, it would be great if your plugin could change the parent by drag-and-drop. You could model it on the way the WordPress custom nav menu editor works. It determines the level of a menu item by its horizontal position. If you want to make an item into a child, nudge it to the right; to put a child item at the same level as the parent, nudge it to the left. That way, the four-way drag cursor becomes meaningful in all four directions, and the resulting interface is very intuitive. If your plugin could do that, it would have absolutely everything I need!
Thanks for all your hard work,