OneNote has to be one of the coolest business applications ever.

It really is. OneNote 2003 was good, though the interface was a bit confusing. OneNote 2007 may be one of richest applications I've ever seen. (Multiple notebooks clinched it for me).

Between writing, research, and client projects, I create dozens of miscellaneous documents a week. I'm disciplining myself to use OneNote exclusively. I'd nominate it for product of the year, and it's still in beta! ;)

Kevin