Thanks for your review Dustin,
I bought this lens this week but have only taken a few test shots and very impressed so far , most of my testing has been at f2.8. Sharpness and Bokeh is amazing.
I have rented the Canon 70-300L before and was impressed with the lens how does the Tamron with a teleconverter compare on a practical basis , I do know you loose 20mm ? Do you know if Canon teleconverters will work on the Tamron?
You'll have to give us your own feedback after you have a little more time with it. It's hard to compare the 70-300L; they really serve two very difference purposes. If you want to travel, the 70-300L is a much better choice as it is far more compact (particularly when fully retracted). It is an awesome lens, very sharp, great color, and surprisingly good bokeh for a variable aperture zoom. The Tamron, for me, serves a very different purpose. It is a perfect event tool and obviously serves the purpose of narrow aperture work.
I didn't test it with the my Canon teleconverter because it worked so well with the Kenko, but I see no reason why it wouldn't work. I should have put it on, but I was traveling a lot during the period I was testing and had multiple events to cover during that time. I would have liked to have had more opportunity to just shoot random stuff, but part of the reason that we chose that time to do the review was specifically because I had multiple professional events to cover.