yeah, i have been on the pak for, well this is my third week. i am in college and i have a ton of work and some days i am going on just a few hours of sleep, and when i i started taking the pak three weeks ago, it about changed my life really. i am not so tired anymore, i have better concentration, and i just feel better all around really. (of course when i get enough sleep i feel even better) i dont know what to say about how it affects me in the gym considering i am stacking it with animal stak2, but i am getting stronger and i am on my third week of this stack. my only complaint about the pak is that it smells so freaking bad. i left the lid off the can on accident one day and my entire room smelled like it, it was horrible. and the smell dosnt just go away, it takes a while. but, its a price i am willing to pay for this great product