I've used the Nite Guard Lites in conjunction with my mutt dogs running around, and they have worked for me. You do have to strategically place them correctly about the perimeter. I have coyotes, bears, fox, bobcat, raccoons, opossums, hawks and owls (including GHO) all living in the forest around my home and barns. I haven't had any losses & mine free range during the day (chickens, guineas & geese). This could attributed simply to good luck or perhaps ONLY the lites or ONLY the dogs or a combination of both dogs & lites.
I also gave a few Nite Guard lites to a friend who was having coyotes running through his yard at night. He said he didn't know if they worked, but the coyotes weren't running through anymore.
Also, I think their effectiveness might depend upon where you live (and this is only a hunch): City predators are used to seeing lots of lights while country predators are not so the Nite Guard lites MAY work better in the country where it is dark and blinking red lights aren't common. The only evidence I have of this is that I used them in the city and I would occasionally have trouble with opossums which in the city, the lites did not deter (I once witnessed an opossum in the city walk up and sniff the Nite Guard lite).
In the country, the only oppossum that got near my place was killed by my dogs. This "country" opossum might have also not been deterred by the lite -- so it could just be an opossum thing.