I like to stack Stimulant X with Hydroxycut Hardcore, pre workout. I can only take one of each, because the comination is extremely powerful. My body temperature actually raises to 100, and I sweat like a fat man chasing a run away twinkie through a Wal-mart parking lot.
The serious side effect that I've noticed is that it kills my appetite. I actually have to be very aware of what I'm eating, so that I eat enough. I've started using gymjournal.com to track nutrition and weight training. It helps to show me where I am with nutrition throughout the day, so I know what I need to eat more or less of.
But if you have appetite control issues, I would suggest stacking the two (or stacking Stimulant X and T-rex, unless you're pregnant.)
These are all powerful fat burners, and coupled with great diet and nutrition, you will see huge fat losses in about a week.