I use them routinely throughout the year for local restaurants that we like, and always check before traveling to see if I might want to use one in that location. I buy gift certificates when they are having a 50-60% off sale (usually 1-2 times per month), then hold them in my account to order and print the actual restaurant certs just before I need them. Once or twice a year in the past they have had 70% off sales! Check the S.P.A.M. forum for the discount codes, or sign up for restaurant.com emails and they will send them to you.
Only twice have I had a cert and when I went to use it the restaurant was no longer accepting them. A quick call or email to restaurant.com and my account was credited immediately.
I have given the gift certs as gifts frequently and they have always been appreciated. They are great as gifts to a new college grad or anyone who is moving to a new location.