Cold water should be allowed to sit overnight. If you camp a great deal a filter might be right for you. Water filters produce the best tasting water. Only water filters can remove pollutants from water. Filtration devices are the most expensive alternative.
Water filters can be a bit bulky to carry.
I don't think so. Many recreation facilites offer water that is not potable. This is water for washing, showering, and toilets that is not fit for human consumption. Many parks treat their water with the same kind of chlorine you would use in your pool. This kind of treatment is not an exact science.