Did that help?
Yes, to summarize:
1. The common aperture and shutter settings found on cameras were created long ago and are retained for historical reasons, but the actual values used in an exposure are only approximations to the camera settings.
2. For ISO Canon reports only very crude approximations to the actual ISO used. You feel that this is for marketing reasons. I would comment that in fact very few Canon P&S users know or care about ISO, especially low ISO. ISO is nowhere near as important as a buzz word as Megapixels. Mainly highest ISO is touted so that users can take pictures indoors in low light.
The lowest ISO on a camera is important to me since noise is a very big issue for my work and I usually set the camera to the lowest available ISO. Thus I look for a camera with highest lowest ISO, but I doubt that many others are conscious of lowest ISO. A problem for me is that there is no standard for noise level at lowest ISO. So a camera with a high lowest ISO may not produce as low a noise level as I might want. I am interested in seeing if CHDK can produce lower noise images than the camera's lowest ISO setting.
Thanks for making it clear.