Sheesh...the Kick-Ich debate again.
It has NEVER, EVER been proven to work. Experts are pretty sure that the majority of cases in which ick cleared up during KI use can be attributed to chance or some other factor. It contains some sketchy ingredients as well, one of which is lovely formaldehyde. In my experience, KI is like Chinese medicine. I lived in China for a time, and whenever you got a minor ailment like a sore throat, they'd say "Oh, you can use some of this ox skin or crushed gold..." but when you're really sick they always say "Oh, you need Western medicine. Our medicine takes too long and once you have severe symptoms it's too late for it to be effective." Etc.
Wanna know my cure for reef ick?
1. Try to buy your fish at least 7-10 days after LFS get them in, reducing the chances that the specimen has ick...provided that you don't see any signs of it in the system either.
2. Quarantine if possible.