A good thread - with some fine examples above.
After one month of use I am very pleased with the Tamron together with my 6D.
I looked for a long time for some longer reach (than my 70-200 f/4 L).
When the new 100-400 still did not materialize, I decided for the Tamron, and got the extra reach as a great bonus. I have a lot of learning to do now with this long reach.
I am pleased with IQ, and especially impressed with the IS/VC.
Also the build seems good to me. So overall value for money is absolutely satisfactory.
This example is one of my favourite objects (small garden-birds) - a nuthatch shot from my open kitchen door (actually this shot was taken by my brother - so all credits ....).
Info: 6D, Tamron @600mm, 1/250s, f/6.3, ISO 800. Cropped.