I placed an order through your web site with my Apple ID (this email address). I attempted to pay for it with a combination of an American Express gift card and my Apple MasterCard. I placed the order on 27 December. Nothing ever happened with it, so I called the customer service line this morning (2 January) to see what was going on. The representative couldn't tell me what the problem was. A few hours later, I got an email saying that the order had been cancelled because the system couldn't handle the combination of cards used.
There are two problems here:
1) The order should have been rejected within a few hours, not a week after ordering. Had it been rejected at that time, I would have re-placed it again immediately. Instead, I waited in limbo.
2) If your system cannot handle a combination of a gift card and a credit card, you should place a notice on your payment options page alerting your customers of that fact so they don't try it in the first place.
As it is, though, I've had some correspondence hanging for a week because I need iWork to finish it, and haven't been able to get it in and installed. This is highly annoying, and not in keeping with Apple's generally good customer service.