I've wanted to try the same thing, but my girlfriend was on it last year, and I thought the food she would bring was gross.
What I have been trying instead is using prepared foods you can buy and figuring the Weight Wtacher points, and making my own "prepackaged meals".
So, I have bought different frozen meals (Healthy Choice, WW, Lean Cuisine), as well as prepackaged food from Trader Joes (primarily their fresh salads, soups, precut veggies and so on) and shelf stable items like 100 calorie packs, South beach diet bars, puddings, 100 calorie popcorn packs, and so on.
I figured the WW points for the items, and basically made a "plan", with 2 frozen meals/salads for main meals, 2-3 snacks and then breakfast food (usually yogurt, fruit, Starbucks latte, etc). I added fresh food like fruit, milk and veggies, just like you have to do on Nutrisystem or Jenny Craig.
Pricewise, it is about the same or cheaper, because I bought on sale. On average, about $5 per 2 frozen meals, and about .50 per snack item, makes it about $6.50 per day, or about $45 per week. Obviously, there is some variance, based on what you eat.
I have been "off the wagon" so to speak, because work has been so busy and I haven't cared too much. But I am jumping back in this weekend.
But this may work for someone
julia