Hi S.,
Many of my friends swear by WW. They found it to be supportive, affordable, and very realistic. They also liked that when we went out, they could still find something to eat, as opposed to more "slavish" diets like no carbs, etc.
I've never heard anything about Slim4Life, but I am like you in that any of those "dietary aids" scare me a little. For one, I don't know exactly how safe they are, and for another, if you need them to lose the weight, what happens when you stop taking them? You can't take them forever...Plus they're usually very expensive.
I myself have now lost 40lbs in the last 6 months using Slim in 6, which is another one of those "as seen on TV" things. It was $70 for the DVDs, flex plan, and diet information. I did NOT use the supplements they offer, nor did I really follow the diet to a T. But, they use this thing called "Michi's Ladder" that basically divides foods into tiers. I like this because if I'm cooking something, I can easily make a choice between things just by looking at the chart. It was a fairly slow weight loss, but I'm still losing about 1 pound a week, even though I stopped the workout program months ago. (It's a 6-week workout.) My husband did it, too, and still uses the DVDs a couple times a week.
Good luck!