I can't say whether or not the product works, but at least it's a natural product! And the literature about it emphasizes that it's meant to work in conjunction with living a healthy lifestyle of moderate eating and moderate exercise, which makes sense to me. This post has more information about what Garcinia Cambogia is.
Honestly I think it's one of those supplements that we're a bit "late" on learning about in the west, as it is a tropical fruit which grows in parts of southern Asia, where people have eaten it for centuries. Now we're catching up, and with the surge of information going around and the interest in Garcinia Cambogia, there are research studies happening, so no doubt we'll have more information about it soon.