We leave soon and we are so conflicted. We are in DW for 10 days. We have done all the calculators and we just don't know which is really worth it. TiW seems like a rip off. You do get the 20% off but have 18% auto added for gratuity. Leaving really only a 2% discount?
Subtracting the percentage of the discount from the percentage of the gratuity is not the correct way to determine the savings on TIW. You need to find the difference from the cost of the meal with the discount, from the cost of the meal without the discount. The late Cheshire Figment used to have a way to describe this perfectly.
In essence, say you make a restaurant purchase totaling $100. (We will leave tax off for the purposes of this demonstration).
Assuming you were going to tip anyway, an 18% tip adds $18 to the total. You are paying $118 for that meal.
If you use TIW on the same meal, subtract 20% from the total. You are now paying $80. Add the same $18 tip and you are paying $98 rather than $118, a difference of $20.
Even if you cut the tip to 15%, you are paying $115 for the same meal as opposed to $98. Now cut the tip even further to 10% (should you be someone who would actually tip 10%). Your bill would be $110 versus $98.
So no, it is not a 2% discount. A 2% discount would have resulted in a restaurant bill of $98 before tip, adding the 18% tip would make it $116. The only way you don't save something using TIW is if you choose to pay an abysmally small tip, or not to tip at all.
I don't know anybody who would disagree that paying $98 is a better deal than paying $118. The question is just whether you would use the TIW enough to recoup the cost of the membership.
There are 10 QS restaurants that will accept TIW. The only park with these restaurants is Animal Kingdom, the rest are at resorts. So if you're planning mostly QS then TIW might not work for you. But with several persons eating at participating table service restaurants for a long trip, it might add up the savings enough.