Well, what can I say. Firstly I should say that I am not Canon bashing, I have been a keen photographer for 40 years and have been using Canon equipment for 20 of those.
I bought the 10D 3 weeks ago. I was instantly aware that after auto focus confirmation, with only the centre point selected, the image in the viewfinder could be brought into sharper focus by turning the manual focus ring slightly clockwise. I had never experienced this with my EOS 5, RT, 1n or D60.
Ignoring this, I spent a few days taking general shots and it became apparent that where I had selected a wide aperture to isolate a subject (I always use aperture priority mode) the results were not focused on the point I had chosen, all lenses exhibiting front focus. For instance auto focusing on the eyes would actually produce a sharp nose. At apertures smaller than f4 the discrepancy could not be seen as it was taken up by the increased depth of field.
I did tripod mounted tests using test targets in the manner suggested on several of these forums and they confirmed that all my Canon lenses were front focusing. At one point I managed to convince myself that I didn't have a problem but realised that this was because I had started to focus slightly behind the desired point in an attempt to convince myself that I had no problem.
I then decided that I was expecting too much from autofocus and what did it matter, because where I chose to use a large aperture I could focus manually. I'm used to this with my Hasselblad 500CM, Mamiya 645 and Leica 11F rangefinder. The viewfinder in the 10D is not especially clear (dioptre adjustment made) and certainly not as clear as the RT or 1n, but nonetheless it is possible to see the relatively sharp point as you focus through it.
Unfortunately, what I saw is not what I got. Turning the focusing ring slightly clockwise and bringing the image into sharper focus in the viewfinder actually produced worse results. By experimenting with incremental manual focusing I found sharp focus by turning the focusing ring anti-clockwise, putting the image out of focus in the viewfinder but producing a sharp image at the sensor plane.
Accepting the limitations of autofocus is one thing but being unable to focus manually (I admit I'm talking wide open) is another. You have to be able to rely on one or the other. So I called it a day and phoned Cameraworld and they exchanged the body without question. My original had an 03 serial number and the replacement an 04 serial number.
The result? The new body has the same front focus problem at wide apertures and the viewfinder has an obvious misalignment of the optical system rendering the top of the screen in different focus from the bottom.
I still love this camera and intend to persevere. I phoned Canon today and they were very helpful. I'm, dropping the camera off at their Elstree service centre and will see what happens.