I can only offer my experiences with it.
WONDERFUL! A must have on any farm, IMO. Use it on the dogs, pig, horses, and chickens. Use it on the garden as well.
Haven't ever had a death, or illness caused by using it.
Again, just going on my experiences having been raised on a farm, and now having my own farm.
It's like with anything though, some will love it, some will hate it.
Research and come to your own conclusions is all I can tell you.
Sevin and Ivomec are two things we always keep here though. Both have been prescribed as treatments by our vet as well. Ivomec prescribed to try to save a dog with severe heartworms, and as preventative for the rest of the gang. Works wonderful in getting rid of worms in the horses, and killing ticks and lice.
Oooopss, sorry... but have to throw in another controversial product.