I've used similar products but not this one specifically. My opinion is that it's bunk. The idea that we're all walking around with "pounds of rotting *" inside us is an absolute myth. Of all the autopsies that have ever been performed, not one single autopsy has ever found "rotting fecal matter" inside a person unless that person had a compacted colon. And if you had a compacted colon, trust me, you'd know it.
This myth is based on an ancient Egyptian idea that all disease came from (a) displeasure of the gods and (b) rotting food in the gut. For some reason it's hung around in natural medicine.
How do colon cleanses work? Well, they're basically fiber. If you're a typical American, you probably eat a diet high in fat and carbs but relatively low in fiber. You probably have relatively small, infrequent bowel movements so when you take a cleansing product like this your bowel movments become much larger and more frequent. People look at that and think "Wow! All that was inside me???" In fact, all they're really seeing is the fiber in the cleansing product bulking up from the water in the gut.
I hope that helps.