I'm amazed at all these people who are disappointed! Maybe, if you are used to straightening your hair, then the swishy, slightly curled effect it gives isn't what you like in your hair? I would say that the picture on the box is misleading. All it does is blow dry your hair with a consistent texture, make your hair shiny and foof it up a bit.
For people who finds it goes flat, I spray this Charles Worthington blow dry styler spray thingy in my hair before I rough-dry it brior to BBHing. It's a heat protection thing as well - and I notice that the volume stays longer using it. Shiny, too.
My hair is very fine, stright on top but corkscrew curls at the end, fairly thick-looking, but I don't think there is actually that much of it - i.e. when I tie it in a ponytail the thickness within the hair band is not as thick as a whiteboard pen, for example. It's very layered and the longest layers reach to between my shoulder blades.
I find the BBH is BRILLIANT for my top layers - defines the layers, adds volume at root, creates a nice even curve throughout the whole shaft. For my curlier and longer under-layers it does not eradicate the natural curl, but definitely helps to 'tame' it and make it look styled rather than frizzy and chaotic. After using the BBH it still looks like my hair, but a groomed version of it.
For a scruff like me, it has been life-changing and I have had a big confidence boost.
Like I said - that Charles Worthington product is worth a whirl.
Sorry - that's a huge post!