I'm still on the fence for this lens
I did try ( hard ) to get closer but I can't between me and the subject I always have obstacles especially water
I guess the only other way it is cropping and / or get longer
I own the 100-400mm and I can get good results when the subject it is pretty close but I notice an IQ loss when used with TC 1.4x
I was wondering if anybody did move from 100-400mm to 150-600mm and regret the change because IQ gain can't really compensate portability loss