there are up sides and down sides to every power adder, nitrous included. ive seen guys who have run bottled cars for years, who have perfectly tuned cars, and mid pass, something "goes wrong" with the nitrous setup....understand that while nitrous is cheap and super effective, it can also be VERY destructive should something go wrong.

ive dealt with a zex wet kit, and had excellent results. the problem is that many people dont have the smarts to wire everything up properly, and if your TPS switch isnt functioning properly and you run lean, it can do alot of damage in a hurry.

also, any forced induction setup, be it nitrous, turbo, or supercharger, increases the wear on an engine, especially one intended for NA use.