Cold hard water has no adverse effects. In fact the high mineral content present is seen by many experts to be beneficial to health. It is only when water is heated, such as in a central heating boiler or in other heating appliances, that problems begin to occur. This is because carbonates begin to react with other chemicals present to form the rock like deposit so familiar as kettle scale.
Although kettle scale may be annoying, the far more serious but less visible effects will be within central heating boilers, hot water cylinders and radiators. If it blocks up your shower head, think what it's doing to the rest of your plumbing!
If precautions in the form of scale inhibition are not taken, fuel bills will be higher, appliance life shorter and maintenance costs correspondingly exorbitant!