This lens, the sigma 24-70 ex dg f2.8 is often overlooked. I have been quite happy with it. The lure of the canon L 24-70 is there but the price tag is not. This lens is around 400 and some change I believe new. Auto focus is a little noisy and slow and hunts a bit in low light however, image quality is great and I keep hanging onto this lens, a true workhorse in my bag.
The canon 5d high iso performance also keeps impressing me. With my old 20d, this would have been rather noisy. I have no fears going up to iso 1600 even without having to use noiseware.
All I did to this image was boost the exposure by .65 (which adds more noise), auto white balance and resized. In my house late this afternoon, Dude up from a nap. f4.5 1/20th of a second, hand held.
edit to add: Had forgotten to take my polarizer off, even sharper without