I've used it, as well as several other "fat burners" in the past. HOT-ROX will provide a nice stimulatory effect IF you respond well to Yohimbine. Some people respond very negatively to Yohimbine and feel real sick when taking supplements such as HOT-ROX that contain it. When I took HOT-ROX I was not able to see a quantifiable measure of fat loss. In other words, my fat loss was the same rate while on it as it was before taking it. This is different from something like EC where I was able to see a measurable difference in the rate of fat loss.
Next, HOT-ROX did not suppress my appetite, which I think is a very important part of a good fat loss supplement. Once again, compare this to EC where I had absolutely no desire to eat while taking it.
Yohimbine does have some scientific backing with regards to "stubborn body fat" which you can find in Lyle McDonald's research or some various Googling. However, if you are above 8% body fat I'm not sure it's going to provide any benefit. The real purpose of Yohimbine in my opinion is getting that last layer of lower ab, or lower back fat off once your fat loss has plateaued several times and you have already exhausted other options.