Valid for 15% off the regular (full) adult rail fare for travel on the Carolinian, Crescent, Piedmont, Palmetto, Silver Star and Silver Meteor.
Valid for sale January 3 - March 11, 2011.
Valid for travel January 10 - March 14, 2011 (with two blackout dates, Feb. 18 and 21).
There doesn't appear to be any advance purchase requirement, and it doesn't appear to affect refundability of tickets. But there's no promotional code and it doesn't even seem to be listed under "Deals" on the website, only on the front page. You have to go
here and click the "Book it Now" button on the right before searching for tickets to get the 15% off.