I've used NO2, and got the same results as others. U get that pump like when u done working out, but only threw out the day, or maybe like 5 hours. i thought it was pretty cool. Its run $79.99 @ GNC tho, way too expensive. u can get it for $46.00 on netrition.com. try it out man.
if u have the mass u should see results
*or u can try NOX2, i've heard well about this too, close to the same shit.