I use Stall Dri and love it. I use it the same way the others use DE. I sprinkle about a cup full into the bedding every week, turn it with a rake or pitch fork, or if the chickens do an awful lot of poo, more often, and let them stir it around when they do their thing. My coop is dry, and doesn't smell, and in the summer had no flies. And, most importantly, my chickens are healthy.
I made a phone call, and according to the company, it does contain food grade DE. I haven't noticed that my chickens go out of their way to eat it, but it's so fine when mixed into the bedding that I'm sure they don't see it as a food.
I've been using it since about May of last year, and have had no sick chickens or problems as of yet.
BTW, I had asked about this product, and a few others, as an alternative to the DE on this message board and received all kinds of warnings and dire predictions from the DE proponents about using anything but DE. Have talked to a few veterinarians, as well as some other people (farmers who have raised chickens for years and years) who have said that there is no evidence that DE is the best or only product you should use for your chickens. DE is not easy for all of us to obtain, and it's expensive as well. Add some shipping charges to it, and it's ridiculous. Don't beat yourself up if you can't use it, just use what other product works for you. Use your own common sense to determine what is safe and appropriate.