Some new docs are up on MSDN regarding OneNote 2003 SP1:

Importing Content into OneNote 2003 SP1 Preview: Learn about the new extensibility features available for developers in Microsoft Office OneNote 2003 SP1 Preview. The new OneNote 1.1 Type Library includes functionality which enables you to programmatically import images, ink, and HTML into OneNote.

Customizing OneNote 2003 SP 1 Using New Command Line Switches: Microsoft Office OneNote 2003 Service Pack 1 (SP 1) features several new command line switches, including switches that you can use to record video notes, import content, and collaborate with other users.