I bought a Groupon worth $85 for $40 and gave it to a couple of friends to go for dinner. The food was good, the dessert apparently was a disaster but what really shocked me is that they told me that they saw the same exact menu as they were getting for $20. So, indeed, I paid the full $40 that the food is worth and got ripped off on the tip, which is based on the "full amount". Another thing: The waitress, who was apparently chewing some gum while serving my friends, ASKED them for $3 more dollars of tip (they have left 10% instead of 15 from the initial amount on the bill).
Boooh never again.