If you use Composition Mode and have set a custom image as the Backdrop, it resets/unsets if you work on the same project on more than one device.
I open my draft on my desktop machine and set a Backdrop image and change the Composition Mode settings. If a few days later I open the same file on my laptop (by using Dropbox, for example), the background image file is not there and the settings have been reset (e.g. the paper Background Fade is back to the default).
I think the correct behaviour should be either:
a) The backdrop image is stored with the project files, so that it can be accessed regardless of where the project is opened; or
b) The backdrop settings are stored on a per machine basis, so you can maintain different settings and backdrop images on different machines (since often they will have different screen resolutions).
Either way, the Composition Mode should not appear broken when moving between machines while working on a project.