The reproducibility of focus on my 7D for some lenses was poor and I had to take many shots to get keepers. The main reason I upgraded to a 5D III was Lensrentals measurements of the consistency of focus showing that the 5D III is much better. FoCal are now publishing on-line the collected results of users on lenses:http://www.reikan.co.uk/focalweb/index.php/online-tools/lenscamera-information/
The ones I know well from experience are borne out in their surveys.
• Variability indicates the range of focus results you might expect. A Low value means most shots will be very close to ideal.
• Accuracy indicates the average focus result compared to ideal – as this number increases, you would expect less perfect focus across a number of shots.
5DIII 100-400mm L Variability = low (3.6%), Accuracy is good (2.1%)
5DII 100-400mm L Variability = significant (11.3%), Accuracy is acceptable (4.4 %)
7D 100-400mm L Variability = significant (13.3%), Accuracy is acceptable (6.0%)
5DIII 70-200mm L Variability = low (3.0%), Accuracy is excellent (1.6%)
5DII 70-200mm L Variability = low (4.2%), Accuracy is excellent (2.6%)
7D 70-200mm L Variability = moderate (4.5%), Accuracy is excellent (2.3%)
Just what I have found: the 100-400L has been given new life on the 5D III, and the 7-200mm L IS pretty good on the 7D and slightly better on the 5D III (the 5D II was thrown in for comparison). It is a useful free tool.