Onenote is an amazing piece of software. For any time of information gathering or note-taking, scrap-booking style brainstorming. Easy to use and plays well with many applications. Never need to save, as it's running in the background using a low level of resources. Easy to copy or move, and very easy to share with others (collaborate as well; so you will see who made changes to what areas). Each page will nicely keep a history of changes where you simply right click on a page, and you can see the many iterations a page has gone through, seeing exactly what changed and when, and select the state of that page from any point in its timeline.
If you use the Getting Things Done philosophy, I find this particularly useful for collection of all non-actionable reference items. Much better than Evernote imo.
The way it is simply set up as a school-type notebook, makes it naturally very logical to use; in terms of what a new book should be, its sections and pages hierarchy, and then a bonus to have pages that can be nested in a hierarchy as well. OCR abilities built in are surprisingly good. The search function is amazing; incredibly fast and accurate.
Those who have never checked this out should give it a try. I truly think that short of Outlook, OneNote should really be the flagship product of Office. If you like Outlook... then Outlook and OneNote are a killer combo!