The Double Down is KFC's most successful debut ever. It has been out for a little over a month and the demand is so high that they are keeping it for longer than the planned 6 weeks. They plan to sell their 10 millionth Double Down soon.
Of course, this makes me curious. If I drive by a KFC and feel like a clogged artery, I may try it. I'm sure it's quite darn tasty.