I have used it and have seen it work sometimes, and other times, it has not. I have not seen any adverse effects to it to any reef inhabitants, however.
I like a product called Stop Parasite a lot more. It is made by a company called Chem Marin and it is a lot more natural. It works on the appetite of the diseased fish, and is more of a nutritional thing rather than chemical. It is also reef-safe, and I have seen far better results to it. The only negative to using Stop Parasite is that a person's alkalinity/kH has to be stable before using it or else the product will effect your pH. Thus, if Kick Ich does not work for you and you decide to try Stop Parasite, pick up a kH test kit and test your kH if you do not know where it is.
While you are treating the fish in your main tank, use garlic and vitamins in his food - Zoe, Selcon, and vitachem is what I would recommend as far as vitamins. You could either use fresh garlic or Garlic Xtreme by Kent Marine. Both have worked fine for me. What I would recommend you do is take the fish's food for a particular feeding, put it in a small cup of tank water, dose your vitamins and garlic, and let the food mix with the vitamins and garlic in the cup for about 5 to 10 minutes. Then, after the 5 top 10 minutes has lapsed, slowly pour the cup with the food into the tank for the fish to eat.
Also, try increasing the fish's feedings to twice a day. However, don't feed anything extra. Just feed less at each feeding, and thus, you will be feeding the fish the same amount, just more spread out rather than in one large daily feeding.
What are you feeding the fish?