It's a great card, especially if you visit WDW a few times a year or for one long visit or you have a large family or you plan to meet up and have a meal or 2 with a few friends Ours has paid for itself over and over.
One of the best perks besides the discounts is being able to valet park at the resorts for free (when dining at a restaurant in that resort).
It is getting a bit pricey though...when it first started the card was a mezzly $25. You could break even in one meal then, now it takes a few meals or a lot of people (up to 6 per meal) to break even and then benefit from the card.
Of course the biggest drawback to many is that it is available to Florida residents only.