We were going to use a Groupon at The Hereford House tonight.
But our waiter was super friendly, provided great service (even got us something currently not on the menu) and quick. When our bill arrived, he had not charged us for my mother's meal, my drink, and he undercharged us for the appetizer that was a special request.
Our bill was a good ~$20 cheaper than we were expecting. Because of the great service, we decided to keep our coupon, and it would entice us to return again in the next couple weeks. So in a way, it worked... but kind of backwards from what they probably expect.
We also left a ~23% tip based on the original value that our bill should have been, too, as we were so pleased.