I rented one of these from a vey reputable shop after my 28-70L was stolen. Now, especially after reading some of the comments here, I can't decide if I really want to buy one or look for a good used 28-70L.
First of all, when I cranked the lens all the way open to 24mm, it "locked up" there. Like there's a light notch in the barrel that intentionally holds it at 24mm. Where my 28-70 was free-flowing and smoothe from start to finish, the 24-70 required an annoying "unclick" effort to get it back out of the "notch" position. Are you guys experiencing that, or did I get a bad lens?
Next off, while it worked fine with available light, on at least 31 frames with this lens and my 580 EX the flash it did not register. I know the flash was going off, and I tried various tests to make sure the flash wasn't malfunctioning. I had to open up the lens to f3.5 at 1/80th and 1600 ISO before the light would register, and I wasn't more than eight feet from the subjects. Even then the images were often too dark. Conversely, when I took the 24-70 off the camera (5D) and used my 70-200 2.8L I got perfect response every time. I finally stopped using the 24-70, since there was no way to rely on it. Anyone else have this problem?
Then there's the whole "bad copy" thing. Paying well over $1000 for a "bad copy" of anything is absurd. Has anyone ID'd the date codes for these "bad copies," and if so, what are they?