I bought this lens from B&H and spent the last two weeks shooting it against the 17-85EFS which it was to replace. It had better contrast and color, but the low light AF hunting and lack of tack-sharp wasn't 500.oo better than the 17-85EFS ( I must have the only 17-85 worth its salt).
B&H is changing it out for the 24-70 2.8 as I write this. We'll see how that one shoots out.
I have to admitt that I'm peeved about the hit or miss quality of the modern lens. It makes it hard to buy one. Do I spend the extra cash and buy locally, where I can test and reject on site, or take my chances and buy snailmail (shipping it back and forth for weeks) or forget the whole thing altogether and use what I have. I thought that manufs would have this lens building thing down pat by now! They're just glass,electronics and machined parts!