The difference (when talking about DoF OR light capturing) between a 300 f/4 and a 300 f/2.8 is significantly larger (both as a percentage and as an absolute) than the difference between a 50 f/1.4 and 50 f/1.2, yet people seem more than willing to sell their mother up the river for the latter. ;)
Oh I am certainly one of those - bring me the Noct 1.2!
It seems like there are four camps in this discussion:
1) Bokeh Kings - The DOF camp.
2) Dark Warriors - Low light camp
3) The AF Speed Demons - Need for AF speed Camp
4) 56ers - those shooting 5.6 and above.
The "night vision" sounds similar to what my sb-900 throws out in low light to focus and is less intrusive than that damn white AF assist light that I always forget to turn off. Niko is right about Sony and I think Canon (at least from film days) used something similar.
My last true AF film camera was a Canon Elan IIe that tracked my eyeball to help with focus. That was about the coolest thing ever and worked quite well for fast action but not so well when I was looking around the frame for exposure points. I often thought that would still be a great feature if it was improved on.
I think the High iso quality and ability to stop down lenses to get additional DOF is a huge plus. Shoot someone at an angle, in low light, with a 85mm and getting both eyes in the focus plane can make or break the photo.