More weight is never better. Period.
If a car handles poorly after weight reduction, the suspension isn't properly set up. Period.
This applies to ANYTHING you want to go faster. Bikes, F1 cars, 370Z's, or a Geo Metro.
With that said, the current Z is lighter than the outgoing model (unless Nissan gave us bad intel last year), and I can attest to the fact that the car handles remarkably well.
Any further [reasonable] weight reduction would NOT negatively impact handling, braking or acceleration.
Period.
