I have been lucky and haven't had any problems with ich. I have heard of quite a few success stories of reefers curing ich by feeding their fish with fresh garlic. The ones that use garlic also say that the bottled garlic preparations are not that effective because the chemical that makes the garlic effective has a short lifespan once the garlic is chopped.
I think I haven't had a problem is that I generally maintain low stocking densities and try to always have at least one cleaner shrimp to keep the bugs off of my fishies.