There are many mixed experiences with this lens,
The first version and the second one(with os), mixed experiences from users who either love it or hate,
Sending them back for failing os/auto focus..
Some find it amazingly sharp, others unacceptable(especially with TC's)
Yet there are a lot of reviews who see this as a serieus alternative to a 300 f2.8 from canon/nikon,
Or an extended 70-200 2.8
Photozone.de was quite positive, especially on center performence (and on crop factor bodies.)
I have also read about thedigitalpicture mid frame and corner results being a bit colored, by the fact that it should perform better when used at a different distance then it was tested.
Anyone that can confirm this?,
If they keep their word at sigma about the quality control, this lens would be a great alternative to the canon 70-200 when used on a crop factor body
Hope to see some thorough reviews when the lens gets released, with real world (high res) examples and crops