Sometimes I would like to make notes and draw shapes over the geometry I'm working on. So I can capture ideas quickly and use them as a reference, in an iterative way.
If you have access to a tablet, whether a PC or a Wacom, it would be easy to add sketches without leaving Inventor.
I'll try and mock up some examples to show what I'm getting at, but I hope others can see the potential in what I'm saying.