No, but I've had battles with B&N over the fact that I had to pop in a c/c to buy e-books with a gift card.Definitely something to look out for, and it will make me give serious consideration to using a pre-paid c/c as backup to the gift card.
If their system is anything like Fictionwise then you just need to update your account details with a valid credit card number. If necessary then redownload the eBook and use the valid credit card number to open the ebook.
Well that doesn't sound overly arduous.
I suspect this is more about them wanting to make sure they have your credit card info than anything. "want your books? give us your personal data, financial preferred"