From a practical point of view what is the impact on photographic quality? I suspect that very few will be bothered to to look at the charts and try to compare with what the see in the actual images.
The shape of the DR plot is of critical importance. With an ideal camera, DR falls by one stop with each doubling of ISO since fewer photo-electrons are collected and read noise is constant. The DR vs ISO plot is linear. However, in many cameras, read noise increases at low ISO and the curve flattens towards the left, limiting DR since what you are gaining at the top (more photo-electrons collected) you are losing at the bottom (higher read noise).
The linear plot characterizes what has been called an ISO-less camera. With such a camera, rather than increasing the ISO setting for low light, you can simply expose at base ISO and correct the exposure in the raw converter. This affords more highlight headroom. When the curve flattens towards the left and shutter speed/f-stop considerations limit exposure, one should choose an ISO where the curve becomes linear. In the example given by
Emil Martinec, that is at about ISO 1600 for the Nikon D3s. Increasing ISO further will lighten the preview on the LCD, but will limit highlight headroom without gaining any DR. This is one area when ETTR according to the camera histogram does not apply. One should still give as much exposure as conditions allow. in order to get a better SNR.
Regards,
Bill