Years ago I spent 30 days at a time in the field, and I was worried about messing up my body's chemistry (many a horror story was told about iodine and the thyroid.). Filters clogged alot back then so I just boiled my water. Now I don't spend nearly as much time out as I use to so I'm not as worried about the chemistry issue and the tablets seem like a reasonable option. I have a friend that worked hunting camps in the Bitterroots. He got away with not treating his water for years. But the little buggers finally caught up with him and man is he paying for it. Giardia may be cureable, but it ain't fun. Why go through that if you don't have to?