I have the original 5d mark I, while loving it, i also hate it. I like to compose using the focus point needed but shooting a reception in dim light or even normal light i just dont trust the outer focus points to work. Although the mark II version was an incredible leap in sensor tech i never wanted one since this frustration with focus would not have been alleviated. The mark 3 not only solves the prob but makes it sports worthy now, That is simply beyond my expectations because I have been forced to use the 5d as a backup to shoot a sports event and was not happy with the focus and tracking but then its a landscape camera. I figured a focus system from the 7d not a 1d focus system. The build, dual cards, waterproofing, low light shooting, the many new buttons allowing most operations to be a click away rather than going thru menus with multiple clicks, and many new features from a software perspective are too good to say no to. I am actually staying put at home waiting for the fedex guy to deliver it today.