Congrats, too, and I am really keen on reading about your first experience with this lens here. Past year I had the opportunity to test the Tammy 150-600 on a Tamron booth with my 5D3 and 7D (Mark I). Optically it was surprisingly good (for such a superzoom) but its AF performance was so bad, in particular with my 5D3, that I decided not to buy it. My wife got one for her Nikon gear, but she has the same trouble with her Tammy's AF performance, MA didn't help much. In the past summer, shooting atlantic puffins in Norway, we met a guy using this Tammy with a 70D, and he said that he stopped even to try BIF.
So I am keen to learn about the Sigma's real life performance! Please, share your experience with us.