There is a Sony Reader page up on the Borders Beta site:
Interesting that they list the $100 classic offer together with the new $50 credit
Now through January 15, 2008, when you purchase the Reader Digital Book you'll receive $50 in eBooks from the eBook Store from Sony at Borders. Offer details below.*
Also, when you purchase the Reader Digital Book before January 31, 2008, receive 100 free classic eBooks. Look for redemption details on the package.
Add to your existing eBook library and save up to 40% off thousands of bestsellers through the holiday season at the eBook Store from Sony at Borders.