I've used these a couple of dozen times, mostly for lunches. ($10 gift certificate for $3...with 70 percent off it's more like $1,)

Just a couple of notes -- if you give them your email address, they constantly send you the discount codes. Each month they reset, so there are usually no or few codes at the start of the month, and then a 50% off one later, then 70% off. I set up a filter to divert these emails into a folder so I don't have to be bothered until I want to buy.

Also, a couple of weeks ago I went to a restaurant that told me they stopped participating in the program in February; however, they said since I had bought it before they stopped participating, they;d still honor it. That seems fair to me. (And that was the first/last time I'm going to that restaurant-- I only went because it mean lunch for two cost about $7.)