NO2 users - do you really feel a difference? if so, how would you quantify it?
I don't know about energy (referring to Eason's comment) but I do feel a difference in the hardness of my muscles throughout the day. My fiancee commented on it as well after seeing my veins and feeling my shoulders she thought I was on steroids (only semi-illegal thing I take is clen right now). It may help with energy but even with no sleep my energy levels never seem to go down so I'm not sure.