Quality construction and reliability. Company has solid reputation making 3D input devices for >20yrs. This type of tool is THE way to save sooo much time if you so a lot of real-time 3D manipulation of CAD models.
though has heavy weighted base, I find it sometimes still slowly slides around on the work surface and gets out of proper orientation. However, the next model up with attached wrist-pad to prevent this, costs ~150$ more (because it also includes more buttons)
Wish I could buy the travel case separately.