So its now time to start the lens sample thread now that the lens is available
Andy Rouse review
Canon 200-400mm f/4 IS: Quick Comparison by LensRentals.com
Dpreview's quick review
Grant Atkinson review
Just a couple test shots done with 1DX.
@560 mm, ISO 400, 1/1250s, f5.6
@560 mm, ISO 400, 1/1000s, f5.6