On Friday I went to the local Calumet and played with a 5D3 for a little. And now I'm saving for one, what an amazing camera. Some shots with a 24-105 f/4L IS:
f/4 ISO 400 (jpeg)
100% crop, unsharpened
f/4 ISO 3200 (RAW)
100% crop, unsharpened
f/4 ISO 25600 (RAW)
100% crop, unsharpened
ISO 25600 is about equal to my 50D at ISO 3200