I used to take a BOSU class at my gym, and it was a killer class. I would walk out of there and my whole body would be trembling because I was using my muscles in a whole different way. It was a circuit workout - along the lines of Boot Camp.
I would buy a BOSU if someone would put out a video like that class. It's entirely doable and would offer a really unique market nitch. If anyone knows of one, please let me know, and I'll bite the bullet (and dodge DH's wrath!).