Boy, with today's quasi-release specifications of 0-60 in 5.5 seconds there sure has been a lot of talk about the accuracy of these numbers. I've put together a small list of what the manufacturer says the car will do, and what the publishers says it'll do:

Car Manufacturer-Specs Car&Driver

Boxter-S (0-62) 5.2 (0-60) 5.3
Corvette Coupe (0-60) 4.6 (0-60) 4.5
M-Roadster (0-60) 5.0 (0-60) 4.5
330i (0-60) 6.4 (0-60) 6.4
TT Quatro (0-60) 6.7 (0-60) 6.2
IS-300 (0-60) 7.3 (0-60) 7.2

Car Edmunds Car&Driver

S2000 (0-60) 6.1 (0-60) 5.8

Based on these numbers, I think we can safely assume the Z will actually be able to do 0-60 in anything from 5.6 to 5.0 seconds. Average that and you've gotten darn close to JmanZ's time of 5.2!!!