One more note, related to the sense of Luxury, and please keep in mind that this has NOTHING to do with IQ or the overall function of the lens.
Tamron completely, massively missed the boat when it comes to the packaging of this lens. This lens was packaged with regular plastic, protected only by cardboard protector. While I realize that this is more "earth friendly", it totally makes it feel cheap. Compare this with the canon, which include its own carrying case (solidly built, worthy of the glass it's trying to protect). They should learn a thing or two from Apple on how to package a product.
One more aspect to consider. The MkII definitely works well with the 1.4x extender, so that will give me the flexibility of going that route, should I choose to. We have limited data on the Tamron, at least with regards to the pixel peeping folks .
The point about the packaging is a good one. In fact, the previous Tamron 70-200 that cost almost half as much came with a decent padded bag that the new lens doesn't. That is one area that Sigma does nicely.
Unfortunately, for me, while I like having those things (like the dumb little "L" series bag/pouch), I don't actually use them. I have padded bags/backpacks etc... that I store gear in - the included bags, pouches, and cases typically end up in the original packaging.