Slim-Fast is not a supplement. It is a meal replacement-and that is a different thing entirely.
I am-and most of the mods here-are against using supplements to lose weight-simply because they don't work and can cause potential health complications due to the ingredients.
Something that I would recommend for those of you starting Slim-Fast-is to try the plan using other brands of meal replacement shakes/bars as well-that may fall in the same caloric range. The Dr. Phil meal replacement bars taste a heck of a lot better than the Slim-Fast ones-and have more fiber, protein, etc. The shakes are the same-over twice the protein-26 grams vs. Slim-Fasts 10 grams, less sugar, and more fiber-8grams per shake vs. Slim-Fast's 5 grams. The shakes have more calcium as well-70% vs. Slim Fast having 40%.
I don't think using a meal replacement is a bad thing at all-but there are some better quality ones out there that you can use with the basic "Slim-Fast" plan that are more nutritious. You can follow the plan the same way though-just changing the shake/bar. As long as it is in the 200-300 calorie range-it can be used in place of the S-F shakes. Kashi shakes and bars are also excellent, more nutritious replacements. Slim-Fast is just the most advertised and popular.
Make sure that you follow the plan exactly though-and DO eat your between meal snacks of allowed fruit/yogurt/veggies. It is an important part of the plan for getting enough fiber and nutrients in each day.
Good luck to you all!
Aphil