We've gotten a large amount of feedback on the ribbon in OneNote 2010 beta.  The Ribbon is a shared component across Office and the owners wrote a good introduction on how to make the ribbon smaller and maximizing your page area.  OneNote should start with the ribbon minimized for this reason and here is their article on toggling it: http://blogs.technet.com/office2010/archive/2009/12/03/minimizing-the-ribbon-exposed.aspx

 Questions, comments, concerns and criticisms always welcome,
John