Very few just use manual focus if their subject moves. A bigger, brighter viewfinder in the upper end of the Canon series helps, as well as, a special manual focus screen to nail shots with thin depth of field. The special composite material that makes up corks apparently contains an anti-focus element which impedes sharp shots. If your trying to get a shot with autofocus and the red square lights up, anything inside and slightly outside that box might be where the camera actually locked focus on. When folks start going with a thin depth of field, they would rather manually rack the focus to where they want. All that said, if your not getting decent shots (sharp), it might be the lens. If the IS goes bad, it's possible to get random shots that are sharp while most are soft. The focusing system is dragging a dead leg with it. Do all your lens act soft or just one? If they all do it, that means it might be the body (yours or the camera) having issues. It might be worth sending it in and having the camera and lens calibrated anyway.