I've had the navigator for a week now, using it with SW and Earth. It works very well and I'd recommend it to anyone who likes to work with both hands. Now I've got the trackman wheel (thumb wheel) on the right side of the keyboard, and the spacenavigator and a three button wheel mouse on the right side. I still use the keyboard for most shortcuts, and for someone with the money to spend it might be nice to have more than two programmable buttons on the navigator.
I use the mouse for most regular windows programs, and the wheel mouse and navigator for SW. It's nice being able to move the model without moving the mouse pointer. It took a couple clicks on the navigator to realize that the buttons move sidways, not up and down.
Overall a nice addition to the desk, heavy enough that it doesn't slide around and pretty stable movement on screen. Now if the boss will just spring for a new workstation in 07.
Diego