And added more.
Look, every new iteration of Windows NT has been more demanding than the previous one.
The change from 5.1 to 6.0 was considered to be to biggest of all, but you should also take into consideration the massive leap in performance when it comes to processors and all. Look what came around WIndows Vista's release time frame: Quad-core processors, price drop in RAM and video cards that are effectively TWICE as powerful as the previous generation flagship GPUs.
Now, look at what's going to be mainstream at 6.1's release: Nehalem, triple-channel memory, SSD drives, further improvements in GPGPU technology and implementation and other things we haven't even seen yet.