I took it for several years, but never more than 1/3 of the dose (this was good ol Ripped Fuel). Make sure it is from a reputable source. I did get very lean using it, but only used it right before a workout and with no aspirin. Also be sure you have no heart or BP problems.
With those cautions, it did work for me, and I didn't regain the weight once I quit using it (just sort of petered out).