It would be nice if there was a mode/template that was tailored around diary/journal writing.
There could be an option for the interface to resemble an actual diary if the user prefers this
You could provide tools to create that personal scrapbook effect e.g frames for pics, cutouts, various paper textures, paperclips etc.
When opening up a notebook created with this mode/template a new page would automatically be generated with today's date, ready for a new entry while still keeping inline with the theme/interface style the user had previously chosen.
It would also be great if there was some sort of drop down box where users could quickly select a date and OneNote would automatically jump to that date and create a new page for that date while still keeping inline with the user's theme.
Holly Field commented
If this had a dairy mode with all dates already loaded, and you could flick through pages and write in appointments and use exactly as you would an actual paper diary it would be awesome!
This is so easy to do as it is, I almost don't see how they can increase the functionality. Name a given page with the date, and then journal away. And to beat the basic "Dear Diary" format, one note includes the ability to add graphics. I have 2 apps on my Ipad specifically for journaling, but the one I use the most is OneNote.