I too must disagree with Chris. You obviously wanted a "loud" exhaust which is the reason you like the Blitz Nur-Spec. I've had both on my car, so yes, I do know.
True the Greddy is relatively heavy but it tucks up well underneath the car avoiding the cheap Pep Boys universal fit.
It's barely louder than stock but sounds so much better. Nice and deep...really brings out the boxer sound.
No, it's not full stainless but it is a quality peice. Keep your underbody clean (however hard that may be :P) and you won't have a problem.
As far as it being the "worst modification" done to your car....well gee....considering it made more power than the Blitz....hmmm, makes you kinda wonder huh?