I just switched from an 03 S2000 to a brand new Z. Loved, repeat LOVED the S2000 (until the con rod went at 72K miles destroying the engine), just so much fun. Took me a while to get use to the Z with totally different power curve, like trying to change gear all the time like I used to in the Honda. I'm probably gonna get shot down in flames but the Z just doesn't feel as fast as the Honda (until you look away from the road and at the speedo - eek !), maybe cos it is bouncing off the redline when the Honda's just getting going. It doesn't scream like the S2000. But, I am in Love with the Nissan. They're both brilliant cars in different ways.
The thing i really miss from the Honda is the massive knight rider style rev counter, why don't you get one of those on the Z.
Anyway you asked about tuning - honestly can't be arsed, as it's fast enough as is. If I want to go proper scary quick I just get my Ducati out :-) ..