I have these, and everyone who's been in the pool likes them a lot. They are rock solid once I got them fastened to the deck. Tried to get by without that, but even with 40# of sand in them they wanted to float around when the kids splashed in the pool.
To be honest I was shocked how much better and more solid they were after I fastened them down. I had to make a small step to go up over the rail so the deck mounts could be fastened down. Wish I had done it long ago.