I use opentable all the time. It's great in big cities like Chicago where they have a pretty extensive restaurant list. I usually mention to the host or hostess when checking in that I made the reservation on opentable and on the few occasions where I've missed a credit, it's quickly resolved. Have never had any problem redeeming for gift certificates - at this point, I've probably used $400 - $500 worth over the course of a couple of years. Much of this has come from taking advantage of the 1,000 reservations (usually off hours) which will instantly earn you $10 of certificates.