I know one lady that did a Costa Rica Groupon deal that had a great time and the place was nice. However, I also saw a segment on TV I think last week on the ABC show The Lookout. They went to a place in the Dominican Republic I believe, and their experience was quite the opposite. They had one of their people book straight through the resort rather than Groupon, and he paid less than they did! Plus, they had lots of problems not getting what was advertised.
I would research the heck out of the place before committing.