I have the Stealth, and NKRO is just being able to press all the keys simultaneously without a lockout. Not particularly important, but it is better than 6/2/1KRO. However, the Stealth has a switching function between 6/NKRO for Mac compatibility. Also, high speed, if what I remember is correct, just means that it polls at 1000 Hz, pretty much standard mechanical keyboard.
Honestly, don't look at it differently from any other keyboard in those factors, but it is a solid board and very good looking. A single complaint might be a lack of rubber feet, but otherwise I love it.