We love it simply for the ease of booking reservations. Most of the better restaurants in town are listed in the system (although rarely as 1,000 pointers). I think I have about 4000 points...a dollar per dinner, not really worth bothering about, but this thread reminded me that I *can* redeem them for a little bit of cash off a future meal.
We also have a local independent restaurant card with points that convert to 10% off. It has much better restaurants than the iDine selection, but about once a year I find a sportsbar type place where I can triple dip...