I posted previously to say that I didn't have the kinds of problems with sand that some people were worried about, like it being too cold in the winter, but it turns out I do have a different problem to report.
This weekend my 5 x 12 sand-filled, covered run, REEKED and turned into exactly the gooey mucky consistency that I had hoped to avoid with sand. This coop and run were built last summer, and housed two hens for late summer/fall, and four since December - so this happened after less than a year of use. I generally raked and removed what I could every week, but apparently left a whole lot behind! That, together with record-level rain and early summer warmth turned out to be a smelly combination. Fortunately I had extra sand that I used to cover the muck and stench. That helped a lot, but there is still a lot of nastiness underneath. Not sure how this will play out.
However, it reminded me that last summer when I decided to go with sand in the run, I read that at least some users of this method replace their sand every year or two. The reason for that is now becoming clear...