Maybe I'm a snob but I only use things specially made for hair. I think it would be okay to use, it won't hurt your hair but normal shampoo would be better. It is an excellent body wash though. Try Aveda for your hair, it's awesome.
I would use it on my hair if it worked, but my hair is dry and I need to use a hydrating shampoo. If your hair is normal or oily and you don't need much conditioner then it would probably work. I know quite a few people that use it as shampoo after the work out or when they are traveling. They don't use it all the time, but I'm sure some people do.