It's quite effective. Over the past two years, I've experimented with Thermicore (original and current versions), Ripped Fuel Extreme, Adrenalin, Lipodryl, Xenadrine, Adipoketix, Lipokinetix, and the original MD6, and with the exception of Adrenalin (original formulation of ephedrine, yohimbine, and norephedrine, which is no longer available), I have found the current version of MD6 to be the most effective by far.
To gain the full benefits of the yohimbine HCL component, take it when your insulin levels are stable. High glycemic foods and supplements that spike insulin levels will reduce the effectiveness of yohimbine HCL. I suggest waiting a minimum of 90 minutes after eating carbohydrates prior to using any thermogenic that contains yohimbine HCL, and waiting a minimum of one hour after use before eating carbohydrates again.
As an aside, I'm currently using MD6 in conjunction with the topical Lipoderm-Y, and I'm seeing excellent results. Good luck...