OneNote 2007 has a very different add-in model. It doesn't even have ribbon, so you can't do galleries like Custom Styles feature has. It also allows a single button in the toolbar for an addin. That is all you get, a single button. Not even a drop-down. You also can't hook up to right click menus, as the image features like Crop etc. does. Overall OneNote 2010 has a much better story for add-ins, so that is what I decided to target.