I'll throw in on Leviathn's side here I'm afraid. The N1K isn't all that special if you run into one alone. Below 10k it might be a very slightly bit better than the Spit IX (it is marginally faster, and climbs marginally better, turns marginally better, and I would assume it accelerates at least as well), but above 10k it is no contest. The Spit IX is definately the better plane overall, in my opinion (although the N1K is definately a good plane).
The Spit IX actually seems to have better vertical performance at low levels, at least thats how it seems fighting Spit v N1K in the DA. The N1K turns a very slight bit better when it gets its flaps down.
How big a threat the N1K is depends on what you are in. All of the US planes except the F4F/FM2 and P40 are faster than the N1K on the deck, same for the VVS planes. The Typhoon is much faster, the Spitfire IX has an even money shot at killing it in a fight, the Spit V can probably kill a N1K a bit more than half the time (especially if the N1K pilot is dumb and turns with the Spit). A Hurricane will probably get Bore N zoomed to death, if the N1K turns with it the Hurri will get an easy kill. Early LW stuff (190a5/a8, 109E&F) are in trouble, the others can run or E-fight.
Overall I'd say the N1K is about as good as a Spit IX (although I personally prefer the Spit, 1 ping kills are tough to beat), so if you have trouble dealing with Spit IX's in your ride of choice you'll have problems with N1Ks too. I think most people do stupid things that get them killed and then blame it on the "super N1K/Spit syndrome".
