I can't help with track impressions since i didn't track either of mine when I had them but here are my thoughts. My 05 with the de motor was a truck motor and tranny for sure. Same tranny found in the frontier and xterra. The car felt really good at about 80% and after that the motor was just really rough and the chassis wasn't happy at the limit. They did fix a lot of that with the 07+ with wider wheels and the hr motor, but it still felt like it wasn't happy when it was pushed. I consider the 350z an 80% car. It wouldn't be my first choice for track unless I got a great deal on one.
And I agree with the c6 opinion posted above. However the earlier model c6's have rubbery steering and I would steer away from those, although overall performance isn't diminished. Nothing quite like a car that was designed a sports car from inception rather than transforming a commuter model into a sporty car
Uzj100, w463, e90 n51, c6 Z06
Recent past: z4m, x5 lci ,m6, boss 302