It can cause impactation, but i have only seen instances of this happening when the snake is fed on the substrate. It doesn't just pass throught because it is VERY abrasive of a product and has very sharp edges.
I use it, i'll be honest. And i feed my bearded dragons on it, but they are the only ones i feed on the substrate. Anything else (hognoses, ball pythins, kindsnakes, whatever) is fed in a seperate container and have had no issues yet.