Good: Scoops like cat litter, it is a natural grit, it doesn't disintegrate when wet, food doesn't get lost in it. You can build sand castles inside, and let the chickens knock it down, or play princess. It is a dust bath. It keeps the chickens cooler in the summer.
Bad: If it is delivered wet like mine, it will never dry. If it is too wet, it will be reeeeeally heavy. It can be compared to cement. It doesn't offer warm flooring in the winter, but as the guy that did the article says, "Chickens sleep on roosts. Not the floor"