Noise doesn't show up in prints, like it does on a lcd monitor, however, contrast is weaker and detail is lost. If I could get good quality images with minimum noise and lots of detail and contrast at ISO 12,800 i would be a huge improvement over my 5D MK II.
I'm sure that Canon only shows images taken with jpeg and huge amounts of NR. They did the same with the 1D MK IV, and when reviewers finally obtained raw images, the real advance over the 1D MK III was about 1/2 stop, but the noise was easier to minimise with NR. With the larger and better sensor, a 2 stop improvement over the 1D MK III using RAW is possible, but, would ISO 12,800 be as good as ISO 3200 on my 5D MK II?
It will be a while before we find out. Having this sensor on a 5D MK III would be great!