While most are not legally binding, there may still be consequences for not complying with the agreed upon portions of the letter. A Letter of Intent is often seen like purchase or crowd-sourced orders, so they are often used to help secure funding or prove the value of the business. If the other party drops out or doesn't honor "in good faith" the letter, actual financial damage may be incurred to the company. In court, most often the judge will make decisions based on what implied intent is expressed in the letter. Sometimes there can be recourse if the parties do not follow through towards an actual legal agreement.
You want your closing statement to be the Mariano Rivera of letters of intent: a clean win, effective, and unambiguous. Don't overthink it! Basic, professional closings are the way to go.