A little background to the comment (all personal, all our opinion)....
We've been getting TIW for about a decade. A GOOD part of this is our desire to go to the better dining establishments at WDW - Signature Restaurants - every night of our vacations. About 20 nights per year.
TIW has, on average (party of two) saved us about $500 per year beyond the cost of the card. It's a true bargain for us.
... and it has one other effect that we value GREATLY. Being a percentage based discount? It does not "force clip" offerings at the Signature Restaurants the way DDP does. I will repeat that these are our observations and opinions - DDP is why finer Disney Restaurants are being destroyed.
This occurs because of the unrealistic "anything on the menu" point approach that DDP currently uses. The backfire effect is simple: Fine Restaurants will NOT put anything, on any menu, greater than a 2 point DDP Compensation. Chefs are forced to live within the DDP walls - and NO ONE may be offered anything beyond that "2 Point" barbed wire.... Folks? It's KILLING a number of otherwise great Disney Owned Restaurants whose career managers "choose" to participate in DDP

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What does TIW do to these fine restaurants? Well, it's a 20% discount - it would be a 20% discount if a restaurant chose to offer a 12 ounce Kobe Steak at $450 a head. It does NOT force-clip Disney Owned restaurant offerings. That same (fairly insane) offering may simply NOT APPEAR on the menu of any Restaurant that accepts DDP... not unless they wish to go broke, very quickly.
You will (and should) choose your dining program based on what is best for you, and your family. In our case? We choose TIW both for it's savings, and for it's positive effect on what we think of as a Family Member - WDW itself. We want those fine Disney Restaurants to STAY that way, and would prefer to NOT have to go off site to find great food.