IMHO an EMS system such as the
Progressive Industries ones are very necessary. They protect against power surges and low/high voltage situations.
On the other hand many people use the autoformers to boost the low voltages that are sometimes prevalent in a campground. In my opinion these just exacerbate the problem for the whole campground. The only reason the voltage is low is because of an overtaxed distribution system and too many people pulling too many amps. An autoformer raises the output voltage by increasing the amps pulled on the input, just making the problem worse for everyone else. If everyone in the campground was using an autoformer, you would have a cascading effect that eventually would blow the main trunk line to the campground.