I've used it for a couple months when I first started, doesn't have any negative side effects from what I've seen. Got good sheds from it.
A few months ago I ran out and just filled the bottle up with water, same results. I never saw any difference. Also got good sheds.
So overall I think it does the same thing water does, except if you keep buying the product you are spending money you don't need to spend.
You get a nice little spray bottle to use to mist when you run out though =).