For me this comparison shows that the Tamron 24-70mm does not even come close to the MK I not even speaking about the MKII if it can deliver what the MTFs show ...
I'm pretty sure he got a bad Tamron sample and will re-test (he got another 70-300L for the same reason) because the iso chart shots contradict everything else said/written about this lens. The sharpness falloff should not be that bad.
But I really hope people will stomp the Tamron into the ground, because then it'll drop in price faster than usual and I can get one :-) ... the only drawbacks to me are really the "onion" bokeh and that its no Canon lens (ie. no cps).