I'm an optician and actually deal with the glasses themselves, rather than the prescriptions. I will say that the opthalmic lenses are at least made by zeiss over here, just completely different division and nothing too special. Nikon, on the other hand, just licenses their name in the US.
Basically, gunnar optics use a special tint (which I can duplicate) and an antireflective coating (that I can get better quality) on a lens that does have a slight add (about +.50) to give you a little "help" up close. That extra add actually can cause some distortion as well, depending on what kind of Rx you have to begin with. Additionally, they use polycarbonate lenses, which suck in regards to optics.
Just seeing what the feedback is both here and a few other places, honestly.