I purchased a one gallon bottle of Dr. Bronner's all natural castile soap in March of this year, and as you can see, I still have quite a bit left. I've been using it to bathe my baby/toddler, and since the soap is concentrated, all it takes is a little drizzle in this(see picture-purple bottle) recycled baby shampoo bottle. I add water to fill about half the bottle, and it's plenty strong enough to wash the hair and body.
I purchased mine from Amazonfor $28.00 with $5.75 shipping when they had a clear-out sale. The price has gone up, but I'll keep an eye on it and post if I see a sale. Dr. Bronner's can be found at health food stores as well; I just couldn't find the gallon containers around my area.
I got the peppermint version because it was on sale. It does sting the eyes a bit, so when I use it on the toddler's hair, I work it from the back of the head forward. I've not had any problems using it this way.
Dr. Bronner's soaps are made with organic oils and are certified to USDA National Organic Program standards. Essential oils are used for the scented soaps. Dr. Bronner's Magic Soaps contain no synthetic surfactants or petrochemicals, and are packaged in recycled plastic bottles. I heard that if you can find a store that carries the soap in bulk, you can reuse the bottle for refills. It's great stuff and thrifty! At this rate, I shouldn't have to buy baby shampoo or soap for years.
I've read good reviewsfrom adults using Dr. Bronner's soap. I just haven't tried it yet because I am still trying to use up a huge stockpile of free-with-rebate and deeply discounted shampoos which I've accumulated.