If you are using DWC.... YES it Can hurt. I've never used it myself (because what I've read), but I've heard from quite a few people that ST is bad in hydro. Something about it directly feeding bad stuff like algae and bacteria (not the benificial kind). I think there's some info about it on Heisenburg's Organic Tea thread.
If you are in hydro, I would steer clear of superthrive.
Also... just a personal opinion, but I think anything that says it does about 1,000 things... and it does it by magic, shouldn't be trusted. Some peeps swear by it though. To each their own.