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.
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.