Visa is SUPPOSSED to contact you, but they really fell short this year and many people learned about "it/discounts" here on the boards. But the discount was released FIRST to the card holders. (I had already gotten in on the
free dining add on for this trip from the bounce back promo last year, unrelated to Visa)
As far as the card goes, when you pay for a package (not a room only) they give you 6 months free interest and no payment, which I guess helps someone who wants to save a bit or even make monthly payments rather than the "lump sum".
Also, you'll get reward credits for your purchases. Before I knew it, we had accumulated an amount that covers our out of pocket for the vacation

(by charging stuff to the room and then paying it off using the reward card)
They also offer some discounts for tours and a free meet and greet character thing at Epcot, which I intend to check out this year (with a free 5by7 pix)
Can't recall anything else.
As far as DISCOUNTS go, I think others here on the Dis may know more ...
hope this helped a bit!