SuperThrive is good to use while plants are in a vegetative growth phase but I would suggest that you do not use it during flower unless you have all the time in the world to wait for your plants finish. One of the things that makes SuperThrive so popular among flower gardeners is it makes flower last longer. It stretches/draws out the length of flowering, which is great for an ornamental, but that is not what most people want when they grow herb.
It isn't damaging and if someone does not mind the extra time to finish flowering buds can end up being larger. They just need to be ready for a few additional weeks (depending on amounts used and somewhat on strain grown) to be tacked onto their finishing time.
SuperThrive is also very good at reducing stress so it is not a bad thing to have around. If your plants suffer accidental damage, shock from various things, etc., Superthrive will help them to come back from it faster and stronger.
Its just not actual plant 'food.'