I have shot a ton of manual images, indoors, low light and good light using autoISO. The benefit, it will choose the lowest and is very accurate. I've used it on a d7100 and d750. Set max of 3200 on the d7100 and 6400 on the d750. I let the millions of dollars expended in r&d on a feature such as this become a tool and I'm not that much of a control freak beyond setting ss/aperture. Shooting events, its very accurate as the lighting and exposure changes. I have total control of ss and aperture which I like. When I use a speedlight, I turn it off. I do spot meter quite a bit indoors. I can prove my point with images I've taken. IF I'm not mistaken, the camera will chose an iso that may not always be available in my menu and is lower than available choices. Since I shoot a ton of events, I don't have time to make changes to my settings. Plus, when shoot action (runway models walking, I'm shooting bursts sometimes and exposure is changing) So, it works for me. shot below in brown was a joint effort by my partner who did a composite for me and the 750. The other, d7100. FYI - shot in bar, taken with the best crop sensor lens I've ever used, Nikon 17-55 2.8. I know its expensive but I bought mine used, it's metal and pro level quality. Here is another shot of a local actor with available light from a window with d7100/17-55 2.8 wide open