Just got the 2X so these are some shots from my first time out with it. AF is plenty fast and IQ is fine. Not as light as the 400 f5.6L but you can't have everything. Cam tracks very well even with busier backgrounds.
Thanks for these samples...very helpful as I consider my own lens lineup.
Results looks really good! Would love some side by side comparisons with primes and the 200-400 for fun, but those are obviously already better than useable.