When used *properly* it works fine. Don't ignore the bit about doing a 20% water change in 48 hours or it can go horribly wrong. I've seen that happen. "Oh... I was supposed to do a water change?"
Often lack of, or insufficient water changes is part of what got a person into Cyano trouble to begin with.
For me a chemical fix is a last resort, AFTER all attempts at fixing the cause(s) are addressed.
I have used, and recommend, Ultralife Red Slime Remover. I have found it to be effective, and much safer. We've even used it in a our 65 with the large Squamosa clam. In 2 days Cyano is gone and stays gone, provided parameters are in check.
If any given tank is loaded with nitrate/phosphate, it's going to come back regardless, because the food is there for it. Hence, address the big picture first before throwing a chemical fix at it, because while it may fix the symptoms temporarily, if the causes aren't addressed you'll be back at square one in short order.
Jenn