The only thing Narga weapons have going for them is that they have great sharpness without Sharpness +1, but I dunno if any Weapon before Megrez's Asterizm (or something like that) is really that useful, but that's because I simply have only really looked at the final weapon.
Also the hidden blade aspect is quite nice in Narga weapons or at least the Long Sword, when you fill your spirit gauge the sword gets another blade and I find the weapon as it's two bladed form quite unique in design. Too bad it doesn't have any game play value.
I use it when I find my elemental weapons not up to snuff, and it has been brutal. It may just be the fact that it is a hammer, but the 20% Affinity and white sharpness usually results in more stuns and knockouts; may also be it is just more noticeable in conjunction with Critical Eye 3.
The high afinity and sharpness can be a boon in high raw weapon classes, like hammer and GS, the narga weapons shine a lot less in weapons that usually count on element to boost DPS, like LS, DS, Lance, and SnS, still good weapons, but not as powerful as others in those classes...
It's better to be thought an idiot than to open your mouth and remove all doubt... "By our blades, the hunters become the hunted..."