Funny you should bring that up. I mentioned it in another topic earlier this evening. I have used it on my beard, but not on my head. (obviously a very white guy). It is mainly marketed to black guys because they have a higher incidence of PFB apparently.
It worked somewhat on my beard, but it was irritating and had a distinct chemical smell. It also left several hairs behind, although they were much weaker and thinner. Not as irritating on the face as Nair. Just irritating to the olfactory senses. And you should not use it for at least 24 hours after a shave because it can irritate the micro cuts caused by razors.
I gave up trying to see if it would be a closer shave than an actualy shave. It is not. And the hair grew back just as quickly. It does not do anything to hair beneath the surface of the skin.
It is good for razor bumps (google pseudofolliculitis barbae) because it severely weakens the short and curlies that cause the problem. YMMV