Amelie, I haven't seen anything about chocolate
sugar-free CW, but they did just come out with regular flavored sugar-free CW (nut'l info here: http://www.kraftfoods.com/main.aspx?...uct=4300001084
I like the SF CW better than the free, even though it does have fat, because they use corn syrup rather than high fructose corn syrup. Truth be told, we're eating such a small amount, it probably doesn't matter.
But if you want to get really nit-picky, the best I've found is the Wal*Mart brand of fat free whipped topping. They use sugar rather than syrups, and they don't use the hydrogenated oils. It's pretty great!