I put sand in my coop in the spring and absolutely loved it. So did the girls. They would dustbathe in it in the sun, and it stayed cool when the weather was hot. I even had it in my nesting boxes, and it kept them cool while they laid and kept the eggs clean.
But, with sand being such a great holder of cold, I just couldn't see them having to stand on it in the winter. So, I put a couple inches of shavings on top of the sand about a month ago (there was only a couple inches left in there), and replaced the sand in the nesting boxes with shavings too. Come spring, I'll shovel it all into the compost, clean, and add all new sand. This is only my first year with chickens, and I am winging it, but I think that's how my yearly rotation will go.