I'd likely consider a Tamron
A Tamron on a 1dx :-) ... beware, the camera might have a built-in self-destruct if combined with 3rd party lenses!
I'm waiting for Neuro to post his opinion and tests. He understands how to do a proper test.
Dr. Neuro said he'd test the Tamron? If so, I'd probably wait for this test too, there are so many different opinions on how fast & precise the af is.
But the most problematic thing about seems to be quality control, that's why existing reviews state that it's either sharper at 24mm or 70mm etc.
It seems like most new reviews are positive but the older ones are pretty bad.
Probably only means that reviewers are afraid to tear a long-term standard L lens to shreds... but then again, manufacturers are known to silently fix issues and optimize the process.