I just bought myself a stock R33 GTR, and comparing that to my stock GTS-T, it pulls much much harder
It takes a bit longer before it gets up and going, but fark, once it starts, it pulls all the way to 8k. The GTS-T was a nicer drive around the city. With the GT-R, turbo's start spooling at 3, and are fully boosting @ 4.5k revs which is a bit high for my driving style. It is more of a race car than a street car, but I absolutely love it to death.
So to answer your question, there is no drop in torque once the GT-R gets into its powerband. It keeps pulling and all you want to do is keep your foot planted while you change gears. Mind you, the first 3 gears are pretty short (180 clicks)