I think two of the most important features of OneNote Mobile are the ability to take photos on WM devices with integrated camera right from within OneNote Mobile, and to record audio notes as well. The images and audio notes are then synced back to desktop OneNote so you have all captured information back on the desktop where you need it. If you take a photo of a document, say a business card, then that image is OCRed when it syncs back to the desktop and all text is searchable by OneNote. That is very powerful stuff. I wrote an overview of OneNote Mobile a few days ago which you can find here:
http://jkontherun.blogs.com/jkonther...andson_ti.html