I've watched a number of videos about the lens, personally, I can't justify the purchase. I use my 100-400 for hummingbirds and the occasional landscape shot. I don't know if I got lucky or not but my copy is super sharp. I might rent one to compare them when it's available.
If you are a current 100-400 owner, what do you think the new lens will do above and beyond what you have now? I know it being f/4.5 is a welcomed, internal zoom, nice but not very nice for travel. The extra weight, depends on the person I suppose. Better AF motors?
To me, I don't understand why they went this direction. Why not refresh the current 100-400 maybe with newer motors, lens coatings, etc. Or a 100-500 F/5.6? internal zoom... GM version?
For those of you who end up buying it, please share your thoughts, I'm sure I'm missing something about the benefits of the lens.
Have a fun weekend all.
Hatch