From:  Michael Gibson
766.6 In reply to 766.5 
Hi Will, the Space Navigator model is really quite compact, it's got a 3 inch diameter circular base.

It actually only has 2 buttons on it, but it has the same kind of twisty knob thing as the higher end models.

Since it is so inexpensive, if you are interested in trying them out it might make sense to get this one first to see if you like that navigation method.

For the models with extra buttons, you can set up the buttons to generate different keyboard shortcuts, I don't think they really do anything else special like change the navigation or anything like that.

- Michael