Our own Photo Wizard Charlie White got his hands all over the Canon EOS-1D Mark III at PMA'07 and was blown away by this $4,500 wonder. And rightly so, because the camera is amazing... except for one little problem.
Imagician Rob Galbraith has been field testing the machine-gun wondercamera and he has detected a problem with the autofocus.
After that, [autofocus in] our preproduction EOS-1D Mark III is a mess. It can't hold focus on static subjects very well and it can't track moving subjects very well. While Canon didn't provide any details about the autofocus limitations we would encounter in the preproduction body, we hope this is what they were referring to and this is what engineers have been solving since.
The problem apparently happens on warm weather and especially bright situations, but it's there and it affects not only the pre-production but also the final production models. Not only that: he has received more than 200 mails with people experiencing the same problems.