the design of the machine is extremely simple, and they generally seem to use the proprietary Fleck mechanism, so I would take the "designer" claims with a pinch of salt.
I have used them for many years. You only need a small drinking-water dispenser. If you keep the main tap in the kitchen sink softened, you will avoid the limescale. The amount of sodium (there is never salt) in a gallon of softened tap water is tiny, much less than in coca-cola or a teaspoon of ketchup.
I like a big machine, it just means you have to fill it up less often as it can treat more water between cycles.
The sacks of salt, I now get 10kg bags which work out slightly dearer than 20kg, but are easier to carry and store. Never carry salt in your own car, a single spilled crystal will eat a hole in the floor. Look inside the delivery van and you will be shocked.
You must have softened water for your washing machine, but hard water for the garden tap. If you wash the car in softened water is will come cleaner and shinier, but there is a slight cost in paying for the softening.
Windows and mirrors are much easier to clean with softened water as it does not leave lime or watermarks. Your towels will be soft and absorbent. You won't need fabsoft, and only half the Persil. Within a month you will find yourself looking at women's hair and thinking "she hasn't got a softener." Try not to say it out loud.