Hester, I don't have one now as we have moved to a property with its own water supply but I came from an area with a very hard water supply. We had a water softener there, it wasn't cheap, although I can't remember how much it cost.
You have to keep them topped up with salt. We used the ones that take salt blocks and had the blocks delivered.
The softener definitely makes a difference although it doesn't get red of the lime scale completely. I didn't go to the bother of having a drinking tap in the kitchen so we drank the softened water. To be honest I couldn't tell the difference. I wouldn't have done this if I had children though.
We did have a tap in the utility room that bypassed the softener and I filled up the animals drinking water from that.
I don't know what the inside of my washing machine looks like but I have had it for 14 years, through water softeners at 2 properties and now using our own soft water and have never had a problem with it.