1. Does it work under less-used OSs? Linux/BSD..?
2. Is it a proprietary format? Will you be able to open the file in a decade? My text files will be able to be opened, I'm not sure anyone can still open their MSWorks files.
Maybe I'm crazy to worry about opening these files after a decade since using them probably isn't worth while unless you keep up with it. However, I've got files from the 90's that I've been transitioning from machine-to-machine since storage costs keeps getting cheaper.
https://itunes.apple.com/us/app/microsoft-onenote/id78480155...
https://msdn.microsoft.com/en-us/library/dd924743(v=office.1...
it is only about 5% of the size of the Adobe PDF specification and I am sure there are corner cases, but it is not too bad.