i had a stock setup. went from a best of 14.1 to a 13.2. the only thing i did was spray 50 hp of the juice for maybe the first 60' granted i did have a screwed up torque converter but those numbers speak for themselves.
I had an edelbrock v6 universal system. i paid around $500 for it. my only problem was mounting hte solenoids, i wanted to keep everything hidde but it didn't work out... (my fault) if you get a piece of sheat metal (i like street signes...) you can make a small bracket that will hold both solenoids and attach to the drivers side intercooler bracket. pretty good looking set up. then if you put the nozzel on the bottom side of the up pipe it won't be overly noticeable. or be like me and put it on the top and it sticks out. not very sleeperish.
its amazing how well nitrous works. on the street i ran about a 30 shot, it didn't help too much with the power but it cooled the air enough i could get more boost. so yes its worth it.
plenty of people will say more boost is just as good, which it is. but the difference is the boost comes up instantly, the power from boost only and no2 is for most of us comparable.
i do recomend it.