The more I use OneNote, the more I like it. It is one of the coolest and most useful applications I have found.
I find myself using to store all kinds of things. One of the things it does when it installs is add a ‘send to OneNote’ option in the printer selection dialog. This allows anything that can be printed to go into OneNote. Makes it really easy to store coupons, invoices, confirmations, etc. in a more structured (or unstructured) manner. I used to use email for managing my documents, but One Note makes it MUCH more easier to do.