I have known about this vitamin for many years. But for the price, there are better values and better formulas out there when it comes to hair vits. I use Longer, Stronger Hair Vits (a Rite Aid vit I think), Natrol HSN, Nioxin Recharging Complex, and have tried GNC Ultra Nourishair.
I would read lots of reviews on Viviscal, because anything costing that much has me skeptical. You might be able to put together the specialty ingredients with a regular HSN (hair, skin, nail) vit and get as good, or better results. I do not know anyone who uses Viviscal.