I found this article on it, but I can't remember where. Remembering the main points from the article:
1. There's no nutritional education. Basically, you're still eating unhealthy foods that can do damage to your body. Just a little less of them.
2. There's no exercise, which makes it a quick fix. Again, you're just losing some weight. Not getting healthy.
3. As AllCdnBoy said, it only works on people that eat for hunger. Basically, it's supposed to make you feel full, so you'll stop eating. The majority of people that are overweight, are often emotional eaters who eat when they're not hungry or past the point of feeling full.
4. Since there's no lasting change, once you stop using it, the weight comes back. It's about $60 a month to keep using it. That gets pretty expensive. We also don't know the long term effects of it.
5. It's not as natural as it claims to be.
It's pretty much a quick fix that works no differently than a lot of other cheaper appetite suppressants.