I'm using Paper to manage multiple ToDo / Task lists across a large construction project. It works great and has been readily accepted by everyone, they understand it and love the simple clean interface. To date all other collaboration attempts have failed due to complexity/ functionality etc.
I've created a Master Index document with links to all the others and in this document I have a link'Your Tasks' which uses https://paper.dropbox.com/tasks to take the user to a list of all tasks assigned to them across multiple documents. This works well but for me it would be much better if Tasks was a menu item in the sidebar, alongside recents, docs, favourites.
Presently there doesn't seem to be a way of finding / listing your tasks on the mobile app, is this planned?
Finally what would be really great is the ability to list all tasks by person either across a project or perhaps that you have created.