plant growth usualy is fast with good conditions. Im not saying superthrive dosent work, but you'd need a control group to compare.
the directions are on the packet, follow them and it does work well. considering how much it costs and how little you have to use i think superthrive is the best bang for your buck you can buy at a hydro shop. i find it halfs cloning time and improves germ rate of seeds. also seems to help full grown plants when used as a matter of course or when having problems.