Dielectric grease is used as a moisture barrier, to prevent corrosion or rusting. It doesn't conduct, but you will want to put it on all surfaces of a connection. When you tighten down the bolt it squeezes out the grease and forms a moisture barrier.
If you were using it on a connection like the frame piece and crimp lug in Squid's attachment in the first post, you'd apply dielectric grease on the bare metal of the frame, on the top and bottom of the circle lug, on the top and bottom of the washer (if you're using a washer), and on the bottom of the bolt head. Then when the connection is snugged down, all those surfaces will squeeze out the grease and have a good moisture barrier - so, that clean bare metal won't rust, and the connection will remain good.
Excellent post squid. The answer to my question seems to be "It will help if you have a problem." Which brings up another question "Do I have a problem?" I guess I could just spend the $40 on the kit and if I notice no difference, just say it's for my flux capacitor.