That sucks Nissan won't do anything for you.
I really don't have the issue that I can tell. I floor the car all the time from ~2,000 RPM. Actually it's one of the things I like about the car - it doesn't have torque like a V8 or anything but it's not anemic like a 4-banger is, I felt like the V6 is a nice compromise in that regard.
I've never felt it lag at all, except when the traction control has come on (cold/wet/both) and most of the time when I goof around it's after I've driven the car for half an hour or more on the highway, and I tend to pass pretty aggressively, so, you know, oil temps are up to 220 or so. We had NO spring this year so it was up around 100 degrees almost every day this summer since I got it... The car spent a lot of time good and hot.
I do consider myself lucky, for sure. I heard about all the trans issues with the 350Z, too, and I knew about DIGItonium's issue from the other thread... Been really hoping I never experience it and so far I have not.
I mean, I'll put it this way. I like the car. It's not the greatest, but, I do like the car a lot. I wish the brakes got some cooling and it had an oil cooler. I hate to see someone else having a bad time with the car. If I had to put up with the **** you guys are dealing with, I'd be outright raging mad.