Chris Pratley has a write up on OneNote SP1 Preview. This is a huge upgrade and has lots and lots of new features. I've been running it for a few months now and love it.
Here are my favorites:
- Capture Screen Shots and Snippets.
- Scratch Out Gesture for Ink.
- Password Protection of Sections.
- Insert Meeting details from Outlook.
- Data Import API (I am writing two of the PowerToys that Chris talks about) 😉 and collaborating on a nice .NET managed API that hooks into OneNote's API.
- Lots and lots of Inking improvements. Inking feels much more natural.
- Insert pictures and documents.