Used it extensively 'in the field' last week. Thought I'd chime in for those thinking about this lens. In brief:-
- if you're used to a f4 lens you'll notice how slow the AF is in comparison. This may or may not be a problem depending on what your subject is and the type of shots you like.
- Sharpness is quite good as is 'bokeh'.
- Very portable and I can shoot all day handholding (not so with my 500/4).
- Versatile of course, but changing focal length requires a big turn on the zoom ring, which can be a problem if (a) you need to be discreet, and/or (b) you need to do it fast.
Overall though, I feel it's a decent lens for the focal length and quality. It's priced appropriately and is inline with existing competitions. If you shoot mainly static stuff and/or in good light, this lens will perform amicably. If you like action and often work in low-light, it may struggle to keep up, especially if you're used to the performance of a f4 super tele.
Hope the above info of some use to you.
D750, ISO1250, 1/3200th, f5.6, @500mm, 90% full-frame.
D750, ISO3200, 1/400th, f5.6, @500mm, 85% full frame.
D750, ISO3200, 1/60th, f5.6, @380mm, 90% full frame.