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 [[The Page Title I Want]] ), 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.