As of early February 2013, WDW is rolling out parts of the new MyMagic+ system. The new payment pads are installed most everywhere, even at Earl of Sandwich which, by the way, means that Earl's is taking Disney room cards now. A couple of places didn't have their pads in operation yet as of this date and a few were having problems. However, these pads are soon going to be in use for payment everywhere in WDW.
To pay for something you touch your card to the Mickey icon on the pad, then punch in your pin number (you create a pin at resort check-in if you are staying on property). Comments on the new pads... Punching in your pin number is not very secure. The pads are sitting on the counter and it would be fairly easy for someone standing nearby to see what number you are entering. But someone would need the card or the information on it to start charging to your account. If you pay with a credit card, the new pads have a slot for the card and the transaction proceeds as before.
At Animal Kingdom and Magic Kingdom, as of this date, pass holders needed to use one of the few turnstiles that have not been converted to the touch-pad system. Regular ticket holders still use a finger scan along with the ticket and no pin number is used for park entry. At some point, it would seem that pass holders will need to get new cards as it seems unlikely that Disney is going to have two entry systems for very long.
There isn't any real information at this point on how the wrist bands will be used. The current cards must be touched to the payment pad, but will the wrist bands be scannable at a distance? There isn't enough public information yet to be sure. Ordinary RFID scanning could present some security issues, especially if/ when people take the wrist bands out of WDW. The level of security issues depends on what exactly is coded into the bands and how easy it would be to scan them, and that information doesn't seem to be available.