Hello Steve,
I very often will edit songs on the Desktop program. While importing new song's is great in the App, editing on a full screen is still quicker. I also will print to PDF on the Desktop, for hardcopy, as the format is more customizable.
I also use my phone (on the go edits and sets), tablet (for playing) and as mentioned my desktop and my laptop. I do this using the Dropbox and DropSync method we describe in the User Guide. It works really well and changes can be checked on other devices straight away, so layouts can be adjusted if necessary.
By the way the Back-up file (OSB) file appears to just be a ZIP file with a different extension. 7z can open it as is, that rename the extension and the Desktop sound handle it fine if that is the way you want up go. After editing just zip it again, change the extension and import it again. (Not sure how import handles duplicates?)
Let us know if that works for you or if you have any other questions.
Alistair