I got out with my copy on Saturday with my 5DIII. My experience matches others, that as-is, this is not an very effective BIF lens. I actually packed it back in the box with the plan on calling to return on Monday.
Sunday was such a nice day, I gave it another chance. Same results for BIF. But the still photos of nesting and more static birds were very nice. For video, it great as well with either the 5DIII or the SL1 (for that extra reach).
Decided to keep it for now. If anyone has any improved technique for BIF or other with this lens please share. Also I plan to communicate with Tamron and hopefully if enough of us do the same, they will come out with a fix to improve focus.
