I started with sand in my third pen, one I keep for feather-foot bantams. It was so easy to clean and it drained so well that I dug out the other two pens and redid them with a load of sand too.
I only have +- 2 dozen chickens right now, so I am able to scoop out all the pens every day. I just use a cat litter scoop/whisk broom/old bucket - - only takes a few minutes, keeps the flies down, keeps the smell down, keeps feather feet clean, lowers cocci rate, minimizes worm issues, lets me observe droppings for possible problems, keeps me out of trouble.
The only down (?) side to sand is that it's BORING to chickens, except for the dust bathing. I toss out trimmed tree branches with leaves, clipped herbs, and garden greens for them to scratch through and they enjoy that much better than a dry desert.
Hope that helps. I'll go home and try to snap a few pics of my pen.