I dislike my inability in most safari situations to create isolation using it at 400mm. There's nothing wrong with the lens, it's just not for me.You had me until you said you weren't a fan of the 100-400! haha I would like to know your reason behind your not liking the lens. I have been nothing but satisfied and impressed with this lens - and that includes using a 300 f/2.8 and 400 f/2.8. Everyone has their personal needs and tastes, but I don't know why someone wouldn't be a fan of that lens after using it.