I tried one this morning about 4 oz or so of it, and I have to say that I saw a difference especially in my energy level, I workout for about an 1hr before I realized the time, after I had a protein shake and lots of water, I got it from GNC and made sure it dint have so of the stuff you guys mentioned, I dont feel jitters but I do feel like I had a great workout, just read and get as much information that you can before trying anything, thank you for the input guys really helped, I wont use it for every workout but it will be there for the days that I need the extra boost in my behind.