Thank you for sharing your review! There is a synergistic relationship between caffeine and other ingredients targeting transmitter chemistry. A small amount of central nervous system stimulation seems to be able to increase the uptake and utilization of a number of other ingredients. it's worth noting the form of caffeine we use bound to the cerebral antioxidant pterostilbene has very different pharmacodynamics: a much slower release curve and longer half-life creating subtler and more stable effects over a long period of time. Caffeine is one of the most studied performance enhancers (both physically and mentally). Its main features would be alertness, processing speed/reaction time, and time till exhaustion/fatigue. Caffeine is not really a bio-enhancer (i.e. something that increases the uptake and utilization of other ingredients) as much as something that works additively with other nootropic ingredients. As an example, theanine isn't great for the things caffeine shines in but is much better for task switching and sustained focus. The combination of theanine and caffeine tends to bring out the best in both, giving a more broadly supportive blend. Some degree of this is lost when caffeine is removed from the stack, but nootropics such as Cognizin and alpha-GPC offer some of the same features as caffeine. So generally, the caffeine-free would have a bit less of the caffeine features mentioned, however, these features would still be there to some degree. Please reach out to our Customer Support team if you'd like to change your current product subscription at support@neurohacker.com.