SoundGuy...Interesting post about the Surge Guard brand. I was debating about that one, but seems that most on this forum think that Progressive's is better made. I do notice that Progressive shuts off power at low voltage below 104, but Surge Guard goes down to 102. Also Progressive unit states to always use it in the upright position. This may make it impossible to use with an extension cord like you mention. I have had occasional problems with slightly recessed receptacles at campground posts.
Camping World has Surge Guard on sale right now and told me that they sell a $40 (or so) one time replacement warranty (presumably for the life of the unit). That sounded pretty good to me.