My DH and I have done the following tours: Backstage Magic (x2); Undiscovered Future World, Gardens of the World (x2) and Wild by Design.
We liked all of them, and we very pleasantly surprised by the Future World Tour. It is relatively inexpensive, although no snack or lunch is included. It lasted for almost 5 hours and took us backstage in numerous areas. We also received an invite for preferred viewing in Italy for Illuminations.
Recently, the best discount has been by charging it to your Disney Visa card (20% off). Since there is no annual fee for the card, we feel like it is worth it just for the tour discounts.
Of course, when we took the Backstage Magic tour the first time, the best discount was with our American Express card, But then, that was when the tour included the Animation Studio at the Studios!
-- Suzanne