considering the fact it's being compared wide open to a leica and a zeiss prime... i think it holds up kind of alright. (the nikon is sharper than the canon, it's just all messed up in that test) but what do you expect? if you want ultimate sharpness, use primes. period.
the canon L's don't happen to be my favorite lens choice for every application, but at the end of most days they do a pretty decent job in the field.