I checked at my two closest Borders now and they have zero discount on the Sony reader, even for a rewards card holder. Their holiday coupons specifically excluded the reader. Not only that but neither store manager has heard about the $50 credit deal! It does not show on their current or upcoming promotion lists, despite my showing them my Borders beta-site promotion print-out. They had no codes or special CD packages to give away with the readers yet.
All they could suggest is someone at corporate pulled the trigger too early.