Netshop21,
the spaceball saves a lot of time in adding mates because it greatly increases your ability to rotate, pan and zoom which are used so much when adding mates. Instead of rotating the model to see the face I need to mate, then zooming in using the wheel/button on my mouse, selecting the face, then zooming out, rotating, then using CTRL-wheel/button to pan, then zooming in again etc., I can rotate and zoom at the same time with the spaceball, select the face, then zoom out, pan and rotate all at once, then zoom in again, all in one fluid motion. You can even use the spaceball to move/rotate parts in addition to using it for panning/zooming/rotating your view. This helps you get this positioned very quickly.
Even just having some of the spaceball buttons programmed as "Mate", "Move Component" or "Rotate Component" saves a lot of time. It might only save a second or two over having to actually go and click an icon, but it adds up quickly.
Hopefully this helps,
Bob