Dave...thanks, I missed that.
Here is a hands-on review.
http://www.dustinabbott.net/2014/01/...vc-usd-review/
I haven't yet read it all. But the parts that I did read seem to indicate that this is a great lens...for the price.
EDIT---the more I think about this, I think I am in a similar boat as Mark. Now that some real information is coming in, I am not sure this lens fits into my kit. If I didn't already have the 100-400L, I'd probably think about it more. But a 25% drop in resolution from 400 mm to 600 mm. Is that really any better than the 100-400L with a 1.4x TC (560 mm)? I doubt it. Sure there is 2/3 stop of light gained. But, it seems that you have to stop down with the Tamron anyway. In looking at my kit, I could add a $400 item that can be used with other lenses and keep my kit smaller, lighter and more flexible.
Plus, I am looking to increase my IQ from the 100-400L. I am not looking for "similar too." If I didn't already have the 100-400L, I'd probably be more tempted as the 100-400L + a 1.4x TC is >$2,000 vs $1,067. So, I'll keep looking at the reviews and maybe I'll see something that changes my mind. And I hope, if nothing else, this puts enough pressure on Canon to update the 100-400L. Because I think what I'd really like is the refresh of that lens or the a 400 f/5.6 IS until I can afford a big white lens.