Consistent navigation across platforms
Opening one note on a Mac or on a PC in 2010 on a PC in 2013 or in the web app version, the notebooks and sections and pages are often times in different locations. It would be nice if notebooks were always in one place sections were always in one place and pages were always in one place.
This applies to the user interface also. Remember, people use multiple devices, so the software should be neutral and navigates consistently.