I just a had a Bosch engineer replace the heating element on my washing machine, I've had it 3 years and limescale had killed it.
Now I've been using Calgon every 3 months and am in a reasonably hard water area so limescale build up is noticeable. But from what the engineer says Calgon won't help me or most areas that have limescale, due to it doesn't actually break it down, also it won't actually help that much with breaking down fat build up or detergent residue.
He's pointed me at some products that will help, they have ingredients such as citric acid (and others I can't remember) that will remove the limescale, fat and detergent residue build up, and also bad smells.
He also mentioned due to washing on 30-40 degree wash that breaking down the fat and other build up won't happen, so a regular 90 degree wash even without any product will dissolve the fat/scum build-up. Then use this product every 3-6 months to clean the element, drum and seals, and allow the washer to last for many years.
As for a dishwasher, similar products are available, but even putting in a chopped up lemon will help break down the fat build up and leave it smelling fresh!
I'm sure this is old news for some but I have only just had my eyes opened to products that will actually help, rather than go with the marketing of Calgon!
He recommended Calc Descaller for Washing Machines, there's mixed reviews looking around, but similar products are available for cheaper that probably have the same ingredients (unfortunately I don't currently know the ingredients list).