It's not really THAT good of a deal. I just bought two today. The one restaurant was $25 off for $10. But you have to spend $50, it's not good on Fri or Sat and it's only good at dinner, not lunch. So really, you are getting $15 off of a $50 meal.
That said, I did use the Upromise 70% off, which makes it a better deal. Its like getting $22 off a $50 meal. I wouldn't have bought without the 70% off code.
Each restaurant has different conditions, some you only need to spend $35, some are good whenever. Just read the fine print and determine if you are really getting what you believe to be a "deal."
But yes, they are legit....