Thanks for letting me know your experience with the servo performance (I assume on a 5D3?) I have some Star Wars stuff I need to sell too, but it won't be getting me this lens anytime soon!
I liked your images although I didn't sign up for 500px yet and couldn't see the full size images, if there were any. Not to criticize but I would say this lens might be overkill for zoo photography, is that your primary use scenario?
Twas on the 5D3. Based on my 1Dx experiences (alas not with the 200-400 itself) it should perform even better on that superbly capable machine!
No criticism taken regarding if this would be overkill at zoos as the answer would be...depends! I think depending on ones goals (for pay/hardcore hobbyist) this lens could be justified. The zoos out here in Arizona often have large (for a zoo) enclosures and the time of day/year the animals can be hard to see as they are far off seeking shade or hiding from the public. A professional or (rich/dedicated) hobbyist could justify the purchase in time saved (and reduced dust risk) from lens swapping and reduced hassle in not needing to carry multiple bodies. All is relative, I suppose, depending on ones funds and/or dedication. I know I have missed some great shots (zoos and in the field) taking off/adding on teleconverters and/or lenses that the 200-400 1.4x would have captured with a level of sharpness that, in most cases, would have sufficed.
Funny enough I worry that at my desired primary use locales, places like Yellowstone and Africa, I might be better off with a 600 and 1.4x attached. Image quality on my 5D3 with the 200-400 and a second 1.4 attached fails to keep pace with a 600 and a single 1.4x. The versatility of the 200-400 is supremely awesome but, my goodness, the 600 is an amazing lens for those far away shots!
Apologies for sending folk to 500px. I was going to upload my 3 images here but it was late and I was lazy and didn't want to convert raw to jpg to get under the 4096KB max file size. A weak, but honest, excuse! :-)
Sadly I re-assessed my Star Wars collection and, yeah, I think you are right. It won't buy me the 200-400 anytime soon (maybe when Disney released the next one though...). It could pick me up the double-dip-eligible 16-35 2.8 though!