Is it wrong that my first response to those numbers is excitement over the tamron?
That much better than the excellent mark I? With stabilisation? For me it's a no-brainer (unless Canon decide to release a mark III with IS any time soon)
I have been using the Tamron 24-70 for the past week, including one wedding - I am not happy with it. Need serious AF micro adjustments, it is now better but still seems softer than it should be, yes I do know the Mark I was pretty soft. But this Tamron is getting beat(at some focal lengths) by it's own 28-75 that I have and still use. Rather than an arm or a leg I think I am going to sell my Kidney
For the Canon.
Disclaimer- My data is ancedotal- Roger has three copies that he tested and all were better than mark I- he also mentioned the front element falling off. . . and did you see the tear down of the Mark 2 - his words "built to last"
Finally some scums are selling the old version at the new version's price
on Amazon. Be careful, I almost pushed the buy button in my excitement of seeing IN STOCK!