I have read in a number of places that exposing to the right (ETTR) only makes sense at your camera's base ISO, with the justification being that if you are boosting the gain in camera (by raising the ISO), you are negating the benefits of ETTR.
My own experience is very different. I have found that if you ETTR maximally, even at ISO 1600 (on a 5D Mk3), the noise is fairly negligible once the photo has been adjusted correctly.
Obviously the huge benefit to raising the ISO is it gives you much more room to manoeuvre, allowing you to maximally ETTR in situations where it would be impossible at base ISO.
So does it make sense to expose to the right at high(er) ISOs, or to select high(er) ISOs specifically so that you can ETTR?
Note: For anyone else answering, please take it as a given that the ideal is to get as much actual light into the camera as possible. I am interested in situations (in my experience, most situations) where something has to give - you need a fast shutter-speed to prevent motion blur, you need to close up the aperture for more DoF – in these situations where you can't just let more light in, what is the best strategy? To forego ETTR or boost the ISO to achieve ETTR?