As JD76 said, the amount of caffeine was lowered to 140-150 mg per cap. Caffeine content is not the reason that reason that Fat Free doesn't seem to hit you as hard as plain caffeine tabs. Since Fat Free is a much more complex formula, it has supporting ingredients that help spread the effects of the caffeine over a longer period of time. This keeps it from hitting you all at once, but the effects last much longer than they would from caffeine by itself. This also helps control any sort of crash you might experience otherwise.
How has Fat Free worked for you results wise? Has it helped with appetite control and fat loss?