[nebucnaut]

"that's very easy for me to either quickly draw on paper or imagine it in my head"

Good point, but it's only easy to draw or imagine if you already know everything involved. In my opinion software visualization should not just be about visualizing what you already know but instead about providing information that you don't know. So you don't need to go through all of your code files in order to draw that inheritance diagram.

"number of users are not visual"

I think I don't know any programmer who hasn't already scribbled some kind of diagram on a piece of paper ;)