I did it back when it was called Slim 4 Life. I lost 20 pounds after a few months, but was able to keep it off for a while before I got pregnant - which was a goal of mine. I'd been struggling with infertility for 6 years and having lost some weight did help in that process.
I found the program to be very helpful in learning a lifestyle of eating healthy. I've since used what I've learned from there and modified it. It is essentially a dumbed down version of the South Beach diet. It spells out the foods you can eat. You do take a ton of pills each day (appetite suppresent, fish oil, and fat blocker) which can be expensive. And, like the other person mentioned you eat two of their supplement foods each day (bars, drinks, snacks, etc.). You eat all day to get in all the veggies and fruit you need. I had to force myself to eat it all each day.
The hardest part of the program is the first 3 days. (If they still do it this way) - You only eat protein for the first 3 days - no carbs. Then you start the actual program they decide for you based on your body type.
I have PCOS so my metabolism is non existent. I think a normal person would do well with this program. Before the program (in 2005) I used to drink 2% milk, use regular salt, and use regular margarine. I now use 1% milk, light salt, and SmartSource or I can't Believe It's Not Butter - light. So, I feel I learned a great education about food and have made some lifelong changes.
Like the other person mentioned, don't buy everything all at once, upfront. I did this and a lot of it went to waste. I either didn't like it and I wasn't able to continue the program when I became pregnant (and then nursed for 14 months, then became pregnant again and nursed for 13 months....you get the picture).
Added: Are you thinking of going to the one in Coon Rapids? That is where I went. There was one lady that was there that I didn't care for. I enjoyed half of child's sized blizzard from DQ and she nearly bawled me out. I didn't care for that at all. I was thinking at least I didn't eat all of a regular sized one! This is progres! Nope. So, check them out and see how it feels for you. And remember, I went 6 years ago. :)