Live Coil Voltage Levels: Pix

There is a lot of information to be found in checking the primary voltage at the coil with a scope. The pattern should be adjusted to show all cylinders on the screen, then look at each cylinder and make sure the coil voltage is being switched by a very "clean" and precise signal. You can make sure each cylinder is being triggered properly and whether or not there is any distributor wobble, bent shafts, bad lobes, or pickups.
I see people on the forums with misfire problems and they spend days chasing their tail trying to find a problem a scope will show in less than a minute.