The following article contains new features of OneNote 2010.
Share notebook between multiple authors: allows multiple authors to access a shared notebook simultaneously, using shared notebook feature. Whenever authors edit the pages and sections in the shared notebook, OneNote automatically synchronizes the changes so that the notebook is always up-to-date.
Better Sub-Page Management: Pages are now easier to manage because they are added at the bottom of the page.
Sophisticated File Management: OneNote 2010 file format enables new features, such as sharing on the Web, linked note-taking, mathematical equations, and versioning.
Touch Support: With your finger you can scroll and pan around any page in OneNote. For example you can pan around a drawing with your left finger and draw with a tablet pen in your right hand. This creates a model for two handed interaction.
Wiki Linking: You can easily create a link to an existing page or to a new page for a topic. You can do this by just typing the Wiki link syntax (e.g. just type ), or use new page search experience from within the link dialog. This enables you to easily create Wiki like notebooks with lots of cross links across pages.
For a complete list of new features visit Microsoft's Website.