I've been spoiled with the D2X and D200, it would seem, when it comes to AF in low light.
Whether portraiture or night college football, I have never had focusing problems with the older cameras.
Not so with the new D600, which I like very much, though primarily for the newer processing technology.
I did a family portrait set in the family's home recently and found I could not focus with AF without the illuminator assist, which looks like an amateur camera when it lights up. I was using SB-800s for flash, so the AF was in ambient light, which was a typical living room.
In my home studio I am also encountering the same problem, and Manual focus is very touching, even at f/2.8.
Any one else with AF low light problems and with a suggestion?