I also had a chance to play with the 200-400 at NAB last week.
My opinion - its advantage is flexibility; and the optics (at least through the viewfinder) looked very nice. But I have concerns.
If you consider that most will either shoot it wide (200) or long (400) - its a 200 f/4.0 and 400 f/4.0 + 1.4 extender. Is the added convenience worth $10k+ ? For those who need the rapid flexibility not to miss a shot between 200 and 560 (extended + 1 stop), maybe.
The feel was nice - I could handhold it but it is physically long. My biggest gripe was the position of the extender switch. I really would like to be able to flick it while viewfinding but its in the 10:00 position. On a tripod/monopod, not as much an issue.
I think this is going to be a very hot lens and very popular with wildlife and daylight sports photographers. High on my wish list but most likely I'll focus on the prime 2.8's first.
« Last Edit: April 16, 2013, 02:47:18 PM by Arkarch »
Landscape, Event, Motorsports
5DIII, 7D, CPS Member
ZE 21/2.8, ZE 50/2 ZE 100/2, TS-E 24/3.5, EF 70-200 f/2.8 IS USM II, EF 24-105 IS f/4, TC 1.4 III