http://www.washingtonpost.com/wp-dyn/content/article/2010/12/30/AR2010123004477.html
The Auto-Train service, which Mr. Garfield started as a private company but later was absorbed by Amtrak, always catered mainly to "snowbirds" going to and from winter homes in Florida. But I used it a couple of times (both one-way southbound) in the spring or summer, to speed up the D.C. to Florida leg of a one-or-two week road trip including other destinations. Not really cost-effective, but a nice change of pace.