Out of curiosity (as you both clealy use these trackballs), what's the selling point of them, what's attractive about what they do?

To me they look like a giant upside-down mouse, where your fingertips are the working area instead of the mousemat or whatever.  What happens when you want to draw, say, a big curvy line?  Surely that would be a nightmare if you have to hold down a button that isn't moving as the device does, like it does with a mouse. And just to be clear, I'm not knocking a trackball, I know a lot of people like them but I'm buggered if I understand the attraction - I literally cannot think of a single task I could use it for where it would be better than a standard mouse.

I like that it's large and substantially built, I'm all for that, but the concept, I don't get the attraction compared to a mouse.