I have been using Restaurant.com for the past 10 years. After reading the reviews I believe the issues with the low ratings are related to the perception of what your buying.
This is not a gift certificate but a coupon for a discount on your meal. Before going to the restaurant you need to call ahead and make sure they are still taking the certificates. I do this every time and about 25% of the time they are no longer taking the coupons. I simply go back to the website, restaurant.com, and exchange the certificate for either another restaurant or a credit to be used at a later date.
If your expectation is you purchased a gift certificate similar to paying with cash then I can see your frustration but what did you expect for a $25 off coupon that you paid $1-$5 for depending on the coupon code you used to purchase it. If you paid more than a few dollars you overpaid.
The reason the restaurants are leaving the program is this is a fantastic deal for the consumer but not so much for the restaurant. They do not receive any of the money you spent on the certificate. They simply participate in the program for advertising and get new customers. The restaurants are losing money on these transactions so I always tip well to make sure the server is well taken care of.
The availability of restaurants can be very limited depending on your location. If you are in a competitive area you can always find a few good restaurants that quite good bargains. The trick is to purchase the certificates with a good discount. Today on Cyber Monday they are giving a 90 percent discount so a $25 certificate only costs $1. If I do not use this certificate I can always exchange it at a later date.
The deals are getting skinnier lately. It used to be you would only need to spend $35 for a $25 discount or $75 for a $50 discount. Today the best deal is spending $50 for a $25 discount. This is still a very good deal and makes it possible to dine out on a budget or better yet if you are a road warrior on a limited corporate per-diem you can eat well and stay within your budget.
The bottom line is this is a very good program for the consumer as long as you check with the restaurant first before you go and only buy certificates when they have good discounts with the coupon codes, i. E. never pay more than $4 for a $25 off certificate and when they have deals like today, $1 for $25 certificate you should load up for the year.