We have several different Moon Sand kits, and we love them. We have this one, and also the Castle oneMoon Sand Royal Castle, and the amusement park one The Moon Sand Amusement Park Carrying Case. It's fun because it's like playing with sand at the beach, only way better because it doesn't stick to your skin, and molds better than regular sand.
Last year when we got our first Moon Sand kit, we used a big cookie sheet (Texas sheet cake) pan with raised edges to do our projects in, so it wouldn't spill into areas we didn't want it to. This year, however, the Royal Castle moon sand kit comes with this cleverly-designed little tray. It is rubbery, and has a nozzle to blow up the edges (like a raft), so that you have little walls around your play area (about an inch high all around). It makes it a lot easier.
The only drawback I'd say with the moon sand is that if you want to do multi-colored creations, it's hard to then separate the colors when you're done. But there's no way to avoid that.
I would think the age of the child playing with it would make a huge difference in how much you like this. Kids 4 and up know enough not to put it in their mouths or throw it, etc. Under that I wouldn't try it.
I should also mention that these have been big hits as gifts at birthday parties, etc. Hope this helps someone decide!
Oh, and here are a couple other tips for you: the moon sand comes in plastic bags that are not re-sealable. So when we are done with the moon sand, we store it in Play-Doh containers. And we also use lots of the molds for Play-Doh kits to make other things with the Moon Sand. We even use cookie cutters with the moon sand! It's lots of fun. I guess you can tell the kids aren't the only ones playing with it....we have fun building things right alongside the kids!