A former neighbor got a few GCs for her new neighborhood as a welcoming gift and from what she tells me, is a great deal. Obviously it's to attract new customers to places that are only getting the regulars but for her, that suited her just fine.
Fifty percent off (plus gratuities) for decent places, no obvious restrictions, and the restauranteurs pretty much knew where the GC came from so that saved the "I got it on the Internet" explanation. The only down side is you might end up at a place you don't particularly like, but the lesson learned is 50% off.