I found NPP very effective but that being said, I didn't really enjoy the effects. I used 600mg a week and gained 25 pounds in 8 weeks. Huge mass gains. But I held water everywhere like you wouldn't believe and didn't get any strength boost, so for my powerlifting purposes it was a bust.
I think you have to use a lot of this stuff to really get super gains out of it, particularly if you have a bigger frame naturally. I think the guys who get away with low doses are skinnier types. I don't think I would use this drug again, it just adds too much water weight and makes me look terrible after about a month. I bloat way too much on it.