I don't experience any of the obvious "tingling" or signs that's some other people do, but it really does work. It gives me so much more energy. Due to migraines I can only do 10-15 minutes max of cardio at a lower intensity, but with C4 I can easily double the time at a high intensity which is a real improvement for me personally. Love the flavor too! I think it's very affordable for the type of product.