A 7D definitely offers signficant improvement over the 40D, specifically in both a more powerful, faster, and flexible AF system, as well as increased FPS.The other areas (eg children at play) - can be done by both 40D and 7D, but again a definite advantage in 'tricky situations' to the 7D. I have a 7D and know it is capabilities and advantages very well compared to other cameras, as well as it is l