Using auto ISO in your camera will prevent you from learning photography properly. Think about this; in the past students of photography using film in their camera, learn how to properly expose the film without changing the ASA in the camera since doing that was not going to help them to get better photos. Students simply learn how to use the film without having to change the ASA (ISO for your digital camera).
Any student of photography should learn how to capture images under any light conditions without changing anything to auto.

I though about this and find it equivalent to accepting that outhouse privy or covered wagon should be experienced before an indoor loo or a car. You used the tools that were available with film and worked around what today looks like major shortcomings in digital. Auto ISO in particular is valuable to get a good idea if not damn close. it does mean you dont understand or prevent you from learning the expose triangle. To not use it as some right of passage is downright silly. Same goes for the either of the priority modes.

This may be a rant, if so I apologize.

Anyone can shoot Manual for any subject under any conditions and get good results--sometimes. In manual, success ratios are subject dependent. If I have time to set up a tripod, carefully compose the scene, carefully meter the light (can't use TTL meter) bracket by 1/2 stops, then I shoot manual and get a RAW image that I have to PP anyway. Of course I don't do that very often, maybe 3 or 4 times a year so I may not know what I am talking about.

I have always been a hunter. Birds, bugs, animals large and small, things that move. I started with a Nikon F, a Nikon 50 mm f2 and a Vivitor 400mm f5.6, and two rolls of Kodachrome and two mailers. [I[Everything[/I] was manual then. No viewfinder readouts, no TTL metering, settings were dials on top of the camera, to check them you had to take your eye away from the viewfinder. Success ratio: Ones I was willing to project on a screen 1:10-15, ones I would show to a real photographer 1:100, maybe.

I wish that people who make pronouncements on shooting manual would describe the type of image making they do i.e. Landscape, Portraiture, Wildlife, etc. and most important I would like to know what their success ratio is.

Every mode on a camera has a purpose. It's up to the user to figure out which is best in a given situation.

If you understand — REALLY understand exposure — then you will make conscious decisions about which mode to use when.

It takes a balance of four things to record an image:

THE LIGHT on the scene (natural, artificial, or a mix)

SENSITIVITY of the camera or film (ISO)

APERTURE in the lens (f/stop)

EXPOSURE TIME set on the camera (shutter speed)

EXPOSURE by itself involves only aperture and shutter speed. They control how many photons can reach the film or sensor.

PROPER exposure requires all four components in balance *for the effect you want to achieve.* That requires an understanding of interplay among the four constraints. Life and photography are both full of little trade-offs.

Many roads lead to Rome, and many combinations of settings lead to exposure. Read, re-read, study examples, test, test, test, make mistakes, evaluate, recalculate... It's a life long process to learn this stuff, so go out and photograph something!