The material feels like the Crocs foam, and I think it's a bit lighter than a regulation ball. It also squishes down more easily; you can flatten it by stepping on it, though it'll pop right back into shape. It also has different bounce characteristics than a regulation ball, I assume due to its weight and materials.
The biggest downside is that the one I got is slightly out of round, though for anyone playing on a dirt "field", it wouldn't matter that much.
Overall, it's kind of incredible what they've been able to do with it. That said, I wouldn't choose to use it over a regulation ball. But if it's all I had, I'd be glad to play with it.