We use our softened water to top off periodically during the summer months when mother nature isn't cooperating with rain. We are on a well system, so we try to minimize water use as much as possible, though. Our softener system (Hague brand) not only softens water, but removes most of the iron which is present in these parts. Since our softener serves our whole house, we use potassium salt, rather than plain old sodium. It's a bit more expensive per bag, but it works as well and allows us to safely use the softened water for house plants and other purposes. During the summer, our water usage does increase, which means we spend more on salt and have more frequent regeneration cycles for the softener. Luckily, we have the softener discharge routed to septic (safe to do with potassium), which means that water is ultimately not wasted.
We've had no problems through two seasons of use in our salt-water pool.