Ask and ye shall receive.
Since OneNote 2010 has been released as a Technical Preview there have been a lot of user questions about the new file format and data portability between the past version and the new version.
Daniel Escapa from the OneNote team to the rescue with answers. He’s blogged how this all works and for those seeking answers you should check it out.
The good news is that there are options available for converting OneNote 2007 data, continuing to use OneNote 2007 data, and sharing OneNote data with users who may not be moving as quickly as you to the new OneNote 2010.