My wife and I were just discussing TIW a few minutes ago. We usually buy a TIW card (DVC / AP rate). We usually go to HDDR and take advantage of the TIW discount for the 8:30 show. That nearly covers the cost of the card. We had a party of seven one year, and it more than paid for the TIW card.
This year is tricky. We are going in November (just the four of us), and we aren't planning to attend a show. I have four table service meals booked over our seven nights. We are also going in July 2017; we will more than likely go to HDDR on that trip with a party of 8. My wife wants to wait until July 2017 to get the card, but we typically don't go to WDW three years in a row. We'd basically buy TIW for just the single trip.
As other have mentioned, you can also save 20% at numerous counter service locations, which adds up pretty quickly. Plus: booze!
To complicate things, some table service locations offer 10% to 15% off for DVC members or AP holders. If I can save the cost of the $150 TIW card, and still save using other options, I may come out ahead.
I guess it's time to sharpen the proverbial pencil.