Anywayz, I always use MF; still find my pics soft leh.
Can it be that the 350d and 400d use mirrors instead of a proper pentaprism in the camera. (idiotic cost cutting) And they are sadly dim to view.
Any slight misalignment of the mirror position will result in inaccuracies.
With the pentaprism, (as in higher grade DSLRs) you do not have that problem, as the physics of the optical properties of pentaprism does not allow for misalignment or wrong positioning of the mirror.