Super-Thrive is basically Vitamin B1 and Thamine. Thamine is a rooting stimulant that can be used on seedlings as well as newly cut clones. I also use Super-Thrive on any plant with signs or stress from transplant and it works wonders on them. The best part is the smallest amount, one drop, is all this is needed per. gallon of water. Because it contains no active fertilizers Super-Thrive has no chance of causing nutrient burn or any other damage for that matter, so one need not worry about giving it to their plants. Furthurmore, I have seen first hand the vigor Super-Thrive induces in struggling plants and I can tell you it does in fact work.
Super-Thrive DOES NOT increase bud size or yeilds and mind you this is not it's intended purpose. Most people gather this misconception from the advertisment which pictures super large fruit which they then equate to a wonder formula that will make their plants giants... not so. Rather, it is used as a quick and effective cure-all for immature and unhealthy plants.
In light of this, my theory is that Superthrive is a great quick fix for screwups and inexperience but it doesn't increase the maximum yield or growth rate of the plant. I mean if it did show a significant increase in yield...wouldn't we all be using it?