Good experiences with Groupon
I use Groupon deals locally for restaurants and products. I also use it when I travel because you can log in to your account and specify cities you will be travelling to. They automatically send you a daily email with deals for those cities. I'll be in Florida for 2 weeks this winter so I've already purchased a l/2 price bicycle rental in Boca Raton and restaurant deals (usually 50% off gift certificate). The restaurants are different than those listed on restaurant.com. I always do some research to make sure that the restaurant is rated highly on Trip Advisor, Yelp, or Urban Spoon. No guarantees, but it helps and I haven't been disappointed. Last year our cousin bought a certificate from restaurant.com for a restaurant in Florida and when we finally found the location, it was out of business. He got a credit when he got back home.
I was just researching Groupon for a tour package that was offered for Costa Rica ($700 for a package valued at $1400). When I went back to the Groupon website it had sold out!
I looked at the World Resorts International offer when it first came out. There wasn't anything of interest to me. It reminded me very much of EV-Rentals - lots of properties available in off-season locations. For example, there was nothing available for Hawaii or the Caribbean this winter!