ISO 12233 chart results are now available on the Canon EF 24-70mm f/2.8 L II USM Lens Review
Results from two copies of this lens are presented. Lens sample 1 is very impressively sharp/contrasty wide open from the center into the full frame corners save 70mm where it becomes that at f/4. Lens sample 2 is slightly softer in the corners than sample 1, but it is sharper in the center at 70mm f/2.8.
Note that results for the older 28-70 L will also be available soon.