We have one.
I hate it.
The previous owners of our home had a big play set in the backyard. It was really more like a park. It was huge. When they moved they took it with them but left the sandbox that was underneath it. So now we have a sand pit in the middle of our yard. A really big one. And I really would prefer to just have grass. Every time my daughter goes in the backyard she thinks she needs to play in it and she gets so dirty. Don't get me wrong. Some days it's great. She'll play for hours in there. But most days it's just an inconvenient mess. The sand is so old and so dirty. It's been through the rainy season and the pollen season and the weedy season. I would love to get rid of it.
The other day I came across this:
This is what I want. A nice portable sandbox with nice clean sand and a lid to keep out the elements. I've seen these storage bins at the $1 store--although I would probably get one that's a little bit larger. Sand only costs a few dollars at Home Depot.
So one day we'll cover up our sand pit with grass or we'll move. Then I'll make one of these. The thought is very exciting to me.