This is a really nice lens. I'll spare the technical information and go with my initial impressions compared to the first version of the canon 100-400L. I actually own the original version of the lens.
It is hard to directly compare them since I shoot the Sony on an a7 which has much better image quality than the 7D I owned previously. That being said, I do feel that the Sony is the superior lens. It has better sharpness wide, but they are similar stopped down. Autofocus speed is similar and the canon might actually be slightly faster. I prefer the "twist zoom" on the Sony, but the push pull was never a deal breaker for me.
Here are a few pictures taken with the lens, all wide open.
taking off osprey by Daniel Riggs, on Flickr
tricolor posing by Daniel Riggs, on Flickr
wings up by Daniel Riggs, on Flickr
