I received this product last week and decided to give it a try. It is yacon syrup. According to the wikipedia entry it is a "sweetening agent extracted from the tuberous roots of the yacon plant indigenous to the Andes mountains." Basically, it's a sugar substitute made from a sort of potato-type thing. It is currently very popular because it has a low calorie content and rather low sugar levels, making it ideal for diabetics. There was a study in 2009 that a daily intake of the syrup decreased body weight, waist circumference, and body mass in obese women.
There aren't a whole lot of instructions on the bottle. It boils down to "take one teaspoon three times per day." So I did a little Google research. From what I read, it may not be a great idea to start on a whole teaspoon of the stuff right away. Yacon syrup can have a bit of a laxative effect so you may want to work your way up. I started with 1/3 teaspoon and worked my way up. I haven't had any gastrointestinal problems myself. Also, it supposedly works the best if you take it 30-60 minutes before eating. If you decide to use it as a sweetener, there have been reports that the fructooligosaccharides (the sweet stuff) breaks down at temperatures over 248°F so while you can use it as a sugar substitute in your coffee or tea, you shouldn't use it for baking or cooking.
I did not cook with the syrup nor did I use it to sweeten anything. (I don't really drink coffee or tea.) I simply took a shot of the stuff 30 minutes before eating. To me, the syrup tastes like coffee. Other people have said it tastes like molasses but I don't think I've ever had molasses. Either way, it wasn't strong enough to deter me. I can't make a comment on the weight loss aspect yet because I've only been taking it for a few days. It did seem to keep me from getting the munchies after eating a meal so perhaps that is where the big weight drop comes from. In the end, it is an interesting product. I might try to use it to sweeten some tea if I have a sore throat, which is pretty much the only time I drink tea, but I don't think it'll actually replace sugar in our household.