I use it in the chicken area of the barn, and in my kitchen where the ants get in. Yes, it works. Haven't seen an ant in a while, although I have seen a few ooky chicken toes recently...so I wouldn't swear it works for mites. But it seems to work OK for ants.
I wouldn't use it in the yard, though. Don't want to hurt the good bugs.
If you spread de in your garden it will kill your bees which are there to pollenate your plants. It is not worth it. Try to find an organic method that will not harm bees.