I have them, and do not like them. As others mentioned, they are difficult to clean around, tend to grow algae, and require about 150lbs of sand or some other weight to keep them down. Two years ago, one of my sand bags broke in the middle of the season, causing sand to spread across the bottom of the pool. Last year, I tried using bags of river rock instead of sand, which seemed to work a little better, but were still a pain to put in and clean.