Auto ISO isn't quite as simple and wonderful as one might be inclined to think.
I have used it in specific conditions (music in bars) with my D700 and it works very well. But, the problem is that if you look at the meter in the viewfinder, it always shows 'perfect' centring of the meter, and then you are left incapable of using your personal experience to adjust iris or shutter up or down, dependng on lighting: the Auto ISO always adjusts back to the equivalent exposure that it orginally set itself.
In other words, should you want to open up a smidgen you can't do this in effect because then the shutter will be speeded up, and vice versa. It really does become too automatic. Using the exposure compensation system setting control is far too awkward for speedy work, where your fingers on the diaphragm or thumb on the shutter wheel can work so much faster.
Kind of back to the drawing board...
Rob C