I love trying new things when it comes to fitness, as long as they make sense (squats on the Bosu ball? No thanks).
I'd wanted to try an Indo Board since I first saw one in a surf shop a while back. It's basically a board that balances on a roller. You stand on it and see if you can slide back and forth, squat and so forth. It works pretty much everything, especially your core.
So when I spotted one at my gym, I had to try it. I damn near busted my ass. But with a little advice from someone who knew how to use it (start on a surface like the mat where people stretch because the roller moves slower), I picked it up.
How is it? Fun, and it certainly does what it claims to do.