But beyond that, I think it would be hard mentally to make the transition from mouse to trackball. I'm so used to using a mouse that it would feel very awkward for a very, very long time.

I personally believe that I will second that: just like with programs, "one's best tool is the one she's already used to." (Sorry to quote myself... ;) But then again (you all) do not misunderstand me: I'm perfectly fine and at ease with my shiny and polished black Logitech cordless mouse! Only, I factually consider myself a person who uses the keyboard, compared with the former, much more than quite about anybody else I know. (Of course around the world there must be someone who is far better/worse than me...) And then again, the situation described in the root node somewhat increases the keyboard/mouse ratio of my needs.