The best answer I have seen to this question is to look at it in terms of the cost of the total vacation:
TP subscription is roughly 10% of the cost of a single night's stay at a value resort -- how many nights were you staying?
TP subscription is roughly equal to the cost of three park snacks -- how many days are you going? Are you bringing your own snacks, or had you already budgeted some of these?
TP subscription is roughly equal to 20% of the cost of a single adult meal at most character buffets -- Are you doing any of these? For how many people?
TP subscription is roughly 10% of the cost of a single adult park ticket for one day -- how much are your tickets going to cost?
TP subscription is roughly equal to the cost of many counter service entrees and cheaper than some -- again, how much have you budgeted for food over your ? days?
When you look at it this way and add up the total cost of your vacation, if you are planning on going for more than one day or with more than two people then unless you are on the barest of shoestring budgets and hadn't planned to spend money on any of these things it doesn't have to be the most amazing thing since sliced bread. Compared to the whole cost of your vacation it's cheap enough that if you think what it does is interesting to you and might improve your vacation, you won't lose much and might gain a lot by just giving it a try.