How important is it to repair windshield damage?

In a word... very.

Most car owners would consider changing the oil and taking care of routine maintenance to be normal steps taken to keep your car up and running, however most people neglect the windshield. It's important to take care of any windshield damage as soon as possible to avoid the affected area from spreading and in the end costing you a lot more money, time, and aggravation. Just because a stone cracking your windshield doesn't change your cars ability to run, doesn't mean it shouldn't be treated the same as any troubles you may have under the hood.