what is the advantage of traction control on a ford, mercury or lincoln rear wheel drive

Yes it's a good thing to have, absolutely. Here is a very good article I suggest you read: http://media.ford.com/article_display.cfm?article_id=23434

As someone who has logged many hours driving in the State of PA (in the Philadelphia, PA Metro areas primarily) during the winter season, I can DEFINITELY say that Traction Control has helped me from losing control on snowy and icy roads. Not sure WHERE in PA you are, but if you're in a mountainous area (like the Poconos), you'll appreciate Traction Control even more so. However, it's NOT just a winter time thing.....I drive a sportscar during the summer and the Stability & Traction Control help me when I take a corner a bit too fast too! Whew!!

Traction control is standard in the LTC and works well. There are times when you may need to turn it off, ie. going up icy hills or starting from stop on icy roads. The traction control applies the brake of wheels that start to spin making it difficult to proceed on icy roads.