I have been using Superthrive regularly for six months now, and every single orchid has developed new roots and canes/bulbs and is healthier than ever before.
I use it at full recommended strength every other watering. I use a weak solution of fertilizer in conjunction with the Superthrive. They are a good combination. (I can tell the difference from when I was just using fertilizer)
It is relatively inexpensive, easy to find, and I think it does what it advertises.
Just my humble and non-expert opinion.
Chris