Hummm.... I've done them. A few years ago as a panic weight loss thingy. As far as weight loss goes, you'll lose a couple pounds in waste and body fluids, but 2 days later it's back on so it's not a weight loss solution.
If you're feeling bloaty and somewhat toxic (depending on your diet) then I would recommend LOTS of fruit juices!! The truth is if you have the right diet, (fruits, veggies, lean proteins) your body takes care of it all by itself.
Personally... unless your diet consists of junk food, and you plan on not eating anymore junk food, I wouldn't do it. If I were on a 7 day In-N-Out burger binge, I might do the juices, but I personally think the cleansing thing is a waste of money. JMHO