I've been two bottles, a few weeks apart, a few months ago. The guy at the Supplement store recommended it. It worked for me, doing as he said it would. Putting more blood in the muscles for a better "pump", meaning more vascular during the workout, and somewhat throughout the rest of the day!!
Then I was about to buy another bottle, and he wanted me to try MHP's TRAC, which is supposed to do the same thing, but has a few more ingredients in it, including Creatine. I like this product a LOT better. I got the same results from N20, but with a little extra!! ISS's Satur8 is along the same lines as TRAC, and some good stuff.