100% actual-pixels center crops of 70mm shots of rather harsh afternoon sun (sorry, 20 min to 1 hour apart) taken from the shade with a 20D in Parameter 2, best JPEG, no PP, on tripod (sorry, the shots with my original 24-70EX were taken from a slightly different spot), MLU, with center AF square right on the sign, focus confirmed with Katz-Eye Plus Hi-Lux split-prism focusing screen, ISO 100, Av mode with exposure times identical between the Canon and the 24-70EX from fStopJojo (1/1250s & 1/800s), but unfortunately shorter for my original 24-70EX (1/1600s & 1/1000s).
Amazing how different these Sigmas can be (not that it doesn't happen to Canons) in terms of sharpness. My original 24-70EX matches the one from fStopJojo from 24-45mm, but beyond that the latter is noticeably sharper. After sending my original 24-70EX in twice to Sigma USA Service for repair of this softness with no luck, I finally contacted Sigma Japan about it, and they say, "We are going to investigate this problem, we are going to repair your lens and if necessary replace it with a new product." So I sent it off on Nov. 3 and am eagerly awaiting its return!
BTW, I plan to do a shootout sometime between this sharp 24-70EX and a friend's 24-70L, so stay tuned...
For reference, here's the "announcement" discussion for this story of mine: http://forums.dpreview.com/forums/read.asp?forum=1029&message=15640130 I'm still wondering whether most 24-70EX's out there are this sharp or soft like my original and several others I've seen samples of... It would be great to see some crops from other 24-70EX owners out there, especially if you think you have a sharp copy!