German Auto, Motor und Sport just tested the new Porsche GT3.
Here are the test results and some comparison data.

Porsche GT3 (new)
0-100 kph: 4,6 sec.
0-160 kph: 9,3 sec.
0-200 kph: 14,4 sec.

Porsche GT3 (old)
0-100 kph: 4,8 sec.
0-160 kph: 10,2 sec.
0-200 kph: 16,1 sec.

Porsche 996 C2 (facelift)
0-100 kph: 4,8 sec.
0-160 kph: 10,9 sec.
0-200 kph: 17,3 sec.

Porsche 996 Turbo
0-100 kph: 4,2 sec.
0-160 kph: 9,4 sec.
0-200 kph: 14,6 sec.

Mercedes E 55 AMG (couldn't resist )
0-100 kph: 4,6 sec.
0-160 kph: 9,8 sec.
0-200 kph: 14,6 sec.