I think its really dangerous. It seems to have opposite effects. Depending on your scalp type, it madly affects the level of dandruff you have.
For a rare, lucky bunch, it gets rid of it pretty well, but for the vast majority (ie. all) of the people I know who've used it, it just makes it worse.
I use it daily, because it makes my hair absolutely beautiful, but for an anti-dandfruff shampoo, its damaged me. I didn't used to have any dandruff at all, and now I do.