The rerelease Klingon seems like a really good reproduction. I would say outwardly a novice wouldn't really notice much of a difference.
I do think the bodies are different... and of course don't say Mego on them. I don't have my Klingon out at the moment but if no one gets to it before me I'll try to give you some more differences.
One cool thing with the Trek line is they have released some figures that were not part of the original line (Chekov, Sulu, etc.) and even remade the Gorn to look like his screen counterpart instead of the weird Mego hodgepodge that was originally released.