I tried these several months ago; I took them for about two weeks before I had to stop because they caused my heart rate to be elevated. I looked into it and found several others who reported similar things. I think it has to do with the form of horsetail extract they use. My heart rate returned to normal after I stopped taking them.

I will say that as far as my hair, I had 3/4 of a inch after two weeks (I normally get .5 -.75 inches a month) and even though I ended up discontinuing my use at the end of that period I still got a full inch that month.

I will obviously never take them again but I I do think they are worth trying, just be aware of how your body responds. My mom took the remainder of my mine and didn't have any problems (she didn't have the same results as far as hair growth but she wasn't very consistant in taking them).
Hair Stats (CG since 3/31/12)
Type: 3c/b; Density: M; Texture: F-M; Porosity: L-N

Cleanser: DevaCurl Decadence No Poo
Conditioner: DevaCurl Original One Condition
Leave-in: DevaCurl B'Leave-in
Stylers: DevaCurl Volumizing Frizz Free Foam, DevaCurl Beautiful Mess, DevaCurl Flexible Hold Hairspray
Refresher: DevaCurl No Comb Detangling Spray
Finisher: DevaCurl Shine Spray