Although I've never been completely tempted by third party lenses, the Tamron did give me an itch that needed scratching.... However, I've bought into Canon, sub-consciously I feel that I'm compromising not using Canon's greatest asset, it's amazing glass... It's looking like a costly future for me with both the 70-200 2.8 II IS & 100-400 (MkII hopefully) plus the inevitable big white to follow... Oh dear, I've got gas :-/