We have had great success with Restaurant.com so far since finding it late last year. This was just after their 90% off offer on 9/9/09. That is the only time I am aware that they offered 90% off. I am hoping they offer a "buy certificates for only 10%" on 10/10/2010. I will be watching my inbox that morning and buying up several $25 certs for only $1 if they offer it.
We don't have many local places that participate, but always look for places for the areas we are vacationing to.
The current 50% off is only through the end of today, but rest assured, they will have another offer, if not a better one starting tomorrow.