Upload & Sell: Off
One thing I'm starting to notice is that Nikon and Canon may be omitting niche designs that others already do very well; Canon's 70-300 non-L, for example, is a useful optic when purchased on sale, but could use an update, whereas the Tammy is much closer to Canon's wonderful L version. Similarly, I don't expect Canon to produce a 14-24/2.8 to compete with Nikon, when the Nikon can be used with an FX G -> EF adapter with ease, and the loss of AF really is no loss given how that lens it typically used.
And then there's Sigma, knocking their primes and all of their zooms out of their relative parks- even their 'lowly' 17-70/2.8-4 OS | C brings something to the table that the OEMs don't provide, and one can't help but mention their outstanding 18-35/1.8 Art and 120-300/2.8 OS | Sport lenses for which no one has even a remote answer.
This is where Sigma, Tamron, and Tokina thrive, and one can't knock Tamron for beating up on the first-party super-zooms. It's an area where everyone would love to see improvement, and it's an area where Tamron appears especially suited to deliver.