|There is a testimonial letter on their web site, but the web site itself is not professionally done, so I remain wary. (Are links allowed on this board?)
At any rate, I've searched for and found the supposed source of the letter (a real person from the Dept. of Transportation in N.C.) and have e-mailed him for conformation.
If all seems legit I'll order the Ongard sample. I have lots of weeds and brush to clear away and I know poison ivy is present in abundance, and I think there is sumac as well. Prevention would be worth it's weight in gold;)