I've used it, readily available at your local Wal-Mart!
Dose as directed, remove activated carbon from filters. If the initial dose doesn't rid the fish of ich after 24 hours, do at least a 25% water change and redose.
Just be wary as it will stain anything and everything it touches. Your fingers, the wood, the seals of your aquarium turn blue, can also kill smaller sensitive fish, catfish, and invertebre.
I've used it with Cory cats and they seemed to be okay, Ramshorn she mystery snails can tolerate it. Any other shrimp or snails I wouldn't try it with.