With my 40D I have not really noticed any difference in picture quality between 100, 200 and 400 ISO. I therefore tend to set it to 400 ISO for almost all situations (unless I need it to be even faster). I appreciate the benefit of being able to use faster shutter speeds, so as to minimize the effects of camera shake and subject movement, which might result in a wasted shot at lower speeds. Does anyone else feel that way? Am I missing something by not utilizing ISO 100-200?