I have been using this for a few weeks and I notice modest improvements during my workouts and distance runs. I've taken some other pre's that give me too much energy it's uncomfortable (as a bipolar person it can be challenging to find the right balance). I find this one gives me the right amount of focus and endurance, as well as a more stable energy for when I want to push myself. I tend to use ON supplements because they seem to incorporate vitamins and other things that help your body in other ways too. I realize many people want a huge pre-workout boost - this is not the rocket fuel one, so if that's what you're looking for I would not recommend this. However if you're like me and you want something more middle of the road for overall wellness - this one is a great one to try out.