I see the very severe limitations under the " TERMS AND CONDITIONS":
* Valid for parties of 2 or more unless otherwise stated.
* Limit one (1) redemption per customer per month per restaurant.
* Only one gift certificate can be used per party, even if the party is seated at separate tables and/or receives more than one check.

So, say the bill is $75, we redeem $25 giftcert (cost ~ $10 on Ebay). In such case the savings are $15 off $75 - the same as Idine prime 20% off !
Granted, if bill is lower, one saves more, but that goes the other way too; and how often do you know what's your bill going to be?
And, with Idine you choose $$ off or miles, you could double-dip with coupons or other discount programs; if you hate the place - you turn around and go elsewhere. With restaurant.com you're stuck - use it or lose it.
Where's the beef?