Have you tried using the AF taken off the shutter, using a single point, one shot mode, and focusing/recomposing? My AF is never set any other way (except very occasionally, on a tripod or with macro pix, I will choose a point other than the center, and occasionally I will use AI Servo mode with just the center point selected). Any other way, and I find AF to work poorly, even on some of the world's best AF systems like 1D series cameras. Why anyone on the planet would want auto selection of the focusing point, or would want AF control on the shutter is beyond me. There is no conceptual difference between doing this and using manual focus. Working like this, the AF doesn't decide anything for you; it just moves the elements for you instead of doing it with your hand.