ask me how I know
Well, how do you know

Actually, the Niki is like a security blanket I continue to turn to when I become frustrated with the other planes. This is THE plane I probably feel the most comfortable with since it suits my natural style of flying the best. Im an aggressive pilot whos valor frquently surpasses his discretion

As Kieren and Leph have already stated, this is a plane which can kill you quickly due to its ability to hide E.
In terms of performance, it can hold its own under 20K. Above that, the engine just peters out. Under 20K (at least on the deck) it can outrun spits, almost climb with them and almost turn with them. Its accelleration is phenomenal. With nose down, I can go from 150 to 250 very quickly.
This is also a plane, in which I do not fear higher bogies. My typical tactic is to get my speed up above 200mph and wait for the bogie to swoop down on my 6. I wait until he closes to 1.6k and then begin a hard, nose-down break turn which is right on the fringe of a blackout. When the bogie breaks off, I quickly reverse the roll and turn back into the bogie. If Im lucky (and the bogie dumb) I can get a quick snapshot. I then begin climbing again, all the while keeping my speed around 200ias. I repeat this as necessary. After a while, the bogie usually gets impatient and tries to zoom which I have JUST ENOUGH E to follow up and either get a snapshot or he cannot get guns solution and drops back down to gain speed. Since Im slower, I fall inside of his arc and my accelleration allows me to force him defensive.
On coalt merges, I work for the lead turn. I will usually try to get my speed up as close to 300ias as possible and go for a nose to nose merge. About 1.6 out, I do a low-G barrel roll to avoid any HO and as I roll back upright, move into an Immelman verticle lead turn. Im hoping that the bogie underestimated my speed and thinks that he could extend allowing me a snapshot. If he goes into a zoom at the merge, I use the guns evasive description found in the preceeding paragraph. To reverse the fite.
In summary, the plane is best used in a finesse role. Hide your E and wait for the enemy to make a mistake. Of course, its low alt performance also makes is a nice brute force plane as well

G'luck with the Nik....I know I got good luck with it!
-Ding