OK, that is the most responsive timeline I have ever seen.
I just ran my first Premiere Pro 5.5 Cuda test with an NVIDIA QUADRO FX 4800. I imported some RAW Canon 60D H.264 footage, and put it in a timeline, scaled it 50% and added 3 more shots, and it played back smoother and fast than any timeline I have ever seen. Color me impressed.
Premiere might not just replace Final Cut Pro, it might blow it out of the water!