It sounds like it will be a very good lens. Some are reporting issues at the long end, so I'd check that out.
I'm waiting for the eventual price drop to decide if I'll get one. By then,there will be a lot of feedback from users.
Softness, particularly at the edges and 70mm.
Two pretty respected reviewers have seen this. There have been some that claim to have seen the issue in poosts on this forum, but I tend to look to experienced testers with a good track record of spotting issues.
It is undoubtedly a fantastic lens, and there may be some samples with issues, which is why I'm waiting for more reviews to come in. I've had 5 of the old version and they were not impressive. I have high hopes for this one.
Let us know what you see.
I've gotten to look at a few copies. One was utterly stunning 70mm, f/2.8, center frame, others VERY good there but not the match for that one, one was quite noticeably softer (at 70mm, f/2.8, center frame) than that one and noticeably softer than the other two. Even the worst at 70mm f/2.8 was still better than a good Tamron 28-75 at 75 2.8 though and maybe similar to a 70-200 f/4 IS at 70mm f/4 (with the copies I've seen the 70-200 f/4 IS is weakest at 70mm, f/4 though, but still solid). The worse ones at 70mm f/2.8 are softer at 70mm f/4 than the better ones are wide open at f/2.8. The best ones peak in sharpenss, center frame, 70mm, early, the lesser ones there peak later having f/6.3 definitely better than f/4, while the other copies having f/4 sharper than f/6.3 (and f/6.3 a bare trace sharper than f/6.3 on the worse copies).
All copies seemed to place edge DOF at different depths compared to the focal point compared to any other copy, which is a bit odd. If you focused on any given point, edges wide to mid were maybe not so different, some a bit better but whatever, but if you focused on some central object then you might have much more different results in the corners depending upon the scene.