Recently acquired this lens and am very impressed. It was a toss up between the F2 version for $4800 or this one for $779. I won't compare the two however as the quality of the F2 is bar none but on a Canon 5D Mark III this 2.8 version is an excellent combo. It's lack of IS is of no consequence as the lens is rather comfortable to hold and lightweight. Just got this Friday 9-14-12. Here's a first set of pics from a concert I shot on 9/17/12 (this pic was posted elsewhere in the forum under Lenses). All photos are converted from RAW (L) to 1920 JPG then down sampled again to 1024 for this forum. 5D Mark III was set to Manual Mode except ISO set to Auto. It would be far too confusing to have to adjust ISO for the ever changing lights and their intensity. In certain instances (not here) I did use a 580 EX II on a bracket off camera.

Photo 1 EXIF: F3.2, ISO 5000, 1/200s
Photo 2 EXIF: F4, ISO 400, 1/200s
Photo 3 EXIF: F4, ISO 400, 1/200s