8 out of 10 points and recommendedPrice usability weight performanceonion bokeh in specular highlights
First off, I needed a second copy the first was de-centered, "as per your tested sample"......the second copy I received was spot on and indeed sharper across the range....I am sure a better centered test example would provided a improved the reviewers conclusions!reviewed January 25th, 2016 (purchased for $932)
For BIF when panning @600mm it's best not to use VC it just blurs the image, at lower FLs VC works better, for stationary targets the VC is an asset.
At shorter FLs the lens is very decently sharp on APSc and very sharp on full frame (swop reach for magnification/perceived sharpness...DXO) above 450mm things look ls good on the APSc sensor but better on full format.
A lot of birders will use the 600mm FL and I found F9-11 gives sharpest results.
AF is great, fast and accurate.
At "600mm" this lens is very sharp at shorter shooting distances and less sharp at longer distances towards infinity, at MFD the lens is sharp at F6.3.
"Onion bokeh" is a problem when shooting against sparkling water and specular highlights, (economic lens grinding smoothness)..Shoot as close to as possible for sharpest results.
The lens's general handling is excellent, for hand-heldshooting I remove the tripod foot.
I have seen a spec of dust or two which comes and goes, no big deal.
The lens has a dust seal around the bayonet but has "no" further sealing.