Katz's Deli in New York City is the best in the world in my opinion, continually selling the best pastrami anywhere since 1888. Recently, we received a delivery that wasn't at all up to their standards. I politely mentioned that via email, never expecting a response. Instead, a woman wrote me asking, what was the issue (tough meat), and then said they'll send a pound of pastrami and a pound of corned beef as compensation!

Moral of the story: There is no greater opportunity for good will and future business than addressing problems positively. When Bank of America complained to me when I ran a  San Francisco office that someone on my team had done a poor job running a workshop, I insisted on seeing the buyer, told him that we'd run another for free, and when he resisted (fearing another bad experience), I told him to get his best people and I'd run it personally.

It was a huge success and BofA became along-term client, which was certainly better (for them and for me) than simply getting their money back.