i started taking silica a couple months ago when i stopped taking biotin. i stopped biotin b/c after a year and 1/2 it was breaking me out, but i still wanted to take something for hair growth besides my mulitvitamin and omega 3 supplements.
so far i'd say its working just as well as the biotin did, minus the breakouts. I take 500mg every night. its hard to tell exactly how much its helping my hair, but i know that its for sure elping my nails. before biotin my nails were super weak and brittle, and grew really slowly. biotin helped immensely, and after switching to silica my nails havent went back to their weaken state (*knock on wood!*).
i'm sure you'll get other replies though-- i've heard of others who've taken silica and swore their gair grew faster.