I've dealt with two major bouts of ICH... the first time, I listened to my LFS
and used medication. All of my fish died. The second time, I didn't use any medication at all - I turned the heat in the tank up to 84 degrees and added 1 tbsp of aquarium salt for every 5 gallons (my tank, 55 gallons = 11 tablespoons). The ICH disappeared and all the fish lived.
I now keep that tank at 80 degrees or so, and run a lower salt concentration. I haven't seen any ICH since, but will always use the heat/salt treatment going forward.