what do you think of the new fly control product for horses?

Have any of you used the new feed through fly control product? I think it is called Simplifly. It is an insect growth regulator, not an OP insecticide. That means it is not toxic to the horse. It disrupts the life cycle of the flys. I think maybe it has to do with chitin production or something like that. Anyway, I thought it was a great idea and used it all last year with fine results. Then I started hearing rumblings about how it also disrupts the lifecycle of the creatures that break down the manure and disrupts the "circle of life". I am an avid composter and have huge piles of manure everywhere in different stages of composting. I haven't noticed any problems yet. Have any of you guys used this product and what were your experiences. Any problems? I was planning on using it again this year because I was quite happy with the fly control and the fact that it is not toxic.