Just keep in mind that Disney Leased areas (Downtown Disney Shops and Restaurants, etc) do not necessarily take the rewards card.
Call ahead if you need to use the card at a non-park/non-resort place, to verify they take it.
Also, a few of the ice cream stands/popcorn/etc. don't take cards. Most do, but the temp carts that come out when it gets really crowded, or really hot (more soda stands) don't have the readers attached.
Other than that, they take it as cash.