SO, I purchased my Apple Watch using Apple Pay. Between then and now, I had restored my iPhone, which of course wipes out all of your Apple Pay cards. Knowing this full well, I contacted Apple.com's sales support staff and was told that there was no need to worry, because my card was already previously authorized, I did not need to update my payment information. Even if I wanted to, Apple.com would not let me update my payment information - it required a potentially lengthy phone call into them, but since I was told it didn't matter, I didn't call 'em.
Well, late this evening apparently my order was getting ready to move from "Processing Items" to "Preparing to Ship" and my transaction was declined (surprise!). I am now able to change my payment info, but the order is back in the "Processing Items" and the shipment date has been pushed further back.
Great launch, guys!