6D seems to effectivly be 'night vision'
Freezing cold night in Minneapolis, moon is only 1/5 illuminated, and not a lot of light. Standing outside, I can see almost nothing, even with snow on the ground.
Had the 85mm f/1.8 on my 6D, and in Live View, I was able to see a lot more on the LCD than I could with my eye. With an even faster lens (1.4, 1.2, 1.0), it would only be a greater difference.
As ISO sensitivity continues to increase on FF bodies, where will be end up in 2, 3, 4 generations? Will we get to the point where fairly clean ISO 1, 2, 4, 8 million will be realistic? At this point, we'll be able to go outside, at night, and capture stunning wildlife pictures without any other light?
I'm blown away with what the 6D can do, and I cannot imagine if the ISO speeds continue to improve, where we may be in the next 5-10 years.
Thankfully, high-ISO will be a key differentiators between cell phones and stand-alone cameras. This means manufacturers will be pushing this hard, and us as consumers will benefit.