Love the flexibility and multitude of uses!
I just bought this product and I LOVE IT!!! I spent a good portion of a crop I was at a couple of days ago touting the many wonderful aspects of Grungeboard to anyone who would listen!
I have no idea what it's made out of (That part's kinda scary!), but this stuff ROCKS! You can bend it (the hinges can be used as real hinges!), stamp it, ink it, paint it, sand it, distress it, etc., and it will still hold it's shape and texture. About the only thing you can't do with it is rip it, and that's great, since I always end up mangling chipboard flourishes when I punch them out.
BUY THIS STUFF! You won't regret it! =)