I own one, an NSX 5.5x22x56. I also spoke with the owner of Nightforce some years ago...forgot his name, but he was a nice guy. He told me that his scopes have the thickest aluminum tubing. He also told me that Swarovski scopes have better "color resolution" (or something like that), which I understood to mean that the colors seen through a Swarovski scope are more true than his Nighforce scopes. But he also approximately remarked something along the lines of "but when your hunting, what does it matter if a Swarovski scope shows you 'the true shade of brown?'" I believe he also did mention that his scopes are used in the military as well, and that one opposition fighter shot at one of our guys, and that the bullet went through the side of our guy's NSX scope and, although he could not change the zoom, the scope still functioned well and our guy continued to use it in battle.
Based on our talk, I bought an NSX scope. I must admit, it is huge, and it weighs a lot. I have it mounted on a Remington Sendero Stainless Fluted in .300 Win Mag (which is also heavy) in Warne HD stainless rings and bases. This rigs weighs about as much as a small car. I obviously use this only when hunting in a blind, so it just sits there until I'm ready to shoot it. Otherwise, if I walked around with it, then I would be in better physical shape than Lebron James. In any event, my NSX scope is a great scope. The quality is extremely good, and clarity is excellent, the knobs are first rate, and it also has an illuminated reticle that is one of the best that I have ever used (and I own SEVERAL scopes with Illuminated reticles).
If you want a scope that is built like a tank (and weighs like one), then the NSX is a great scope.
Zachary