I'd like to hear opinions on this product also! We just started our two horses on it three days ago....
Our OTTB is a gray, and OTTBs are supposedly thin skinned, being gray makes his skin even more sensitive, we've been told...and he suffers horribly during fly season. They drive him insane, and he is so reactive to their bites(rearing, bucking, bolting) that he is dangerous to be around. He also suffers from severe allergic hives from the bites and is quite lumpy and insanely itchy during fly season. The vet said he may have to go antihistamines if this doesn't work.
Our Belgian mare is much less reactive and doesn't have allergies, but the flies do bother her to the point where she repeatedly kicks at her stomach where they like to congregate, and has twice last summer lacerated her stomach with her hoof.
So, here's hoping this stuff works to some degree......for both of us.