Hi Randy,
I totally know what you mean about questioning the humaneness of invisible fencing. I totally struggled with it too. Ultimately, we made the decision to try it (after I made my hubby run through it, of course!!), and I feel confident that we made a good decision.
We use Petstop and both boys are on the lowest correction level. Like Lin, our fence actually got unplugged for at least a week, and we had no idea! Once the boys learned their boundary, they really don't test the limits at all. In fact, all they really need is the auditory beep that warns them that they are getting close. Because of this, we actually keep their collars really loose (I had a problem with the prongs...I think that they MUST be very uncomfy!).
If I could do it all over again, I would make the same decision; although, it would have been nice to find a system that has a auditory and physical vibration warning....I think I've heard of a system that has this, but I'm not sure which one.