I have already driven the Nismo, but no GT yet.
The Nismo suspension was stiff, but it wasn't so much of a problem. The real issue for me was with the damping (or lack of?).
The car was bouncing a couple of times over its spring each time I was driving over a bump, especially with this level of stiffness. If felt under damped if I'm correct.
Now that wouldn't be so much of a problem with a soft sprung barge, but with firm springs I found this uncomfortable.
I'm sure others will disagree with me, and fair enough I'm no specialist.
Over than that I loved the car. If I could tune the suspension, I would probably consider one over the GT just for the sound it makes.