If you have more than 3-4 gpg of hardness in your water, you'll spend more money to heat water, replace water heaters and/or electric elements and other water using appliances and to wash and replace clothes and fixtures that will wear out prematurely etc. than to buy a softener and maintain it. Of course that means you don't pay gobs more bucks for it than you could have.
All the water used in the house should be treated, not just the water heater cold feed. And there should not be a hard water line run to the kitchen sink, or toilets etc.. The people that think they get a benefit out of drinking hard water need to look up how much water they'd have to drink to get any benefit from the minerals in it. And drinking too much water will kill you.
The added sodium caused by ion exchange softening, if using softener salt instead of potassium chloride (salt substitute) which is not as efficient as 'salt' because all cation softening resins are made in the sodium form, is 7.85 mg/l (roughly a quart) per gpg of exchange. Thirty five gpg = 274.75 mg/liter (or quart).
Most of us are npt drinking the 8 8oz glasses of water we are supposed to so how many are ingesting a quart of softened water a day?
An 8 oz glass of V8 is like 560 mg of sodium. Same size glass of skim milk, about 530. A slice of white bread, from 120-160 mg. On'n on. Some people could eat a few less chips or other snack foods and drink a gallon or more of their softened water and actually REDUCE their daily sodium intake. But they see all that salt they pour in their salt tank disappear and mistakenly think it all went into their water. It doesn't. A softener only uses a small amount of the sodium, all the rest and all the chloride goes out the drain line.
People on sodium restricted diets know how to count their daily uptake and can adjust accordingly. Healthy people get much more sodium than the body requires but drinking softened water doesn't add near as much as some would have us believe.
BTW, all waters contain some sodium to begin with, check your water company's water quality report or have a sodium test done on your well water and see.
The vast majority of people with water softeners say their coffee and tea tastes better or there is no difference. Hardness (calcium and magnesium) is a small part of all the stuff in the TDS (total dissolved solids) content of a water. They cause taste problems much more easily than hardness does.
Gary Slusser Quality Water Associates