To me, the requirement some seem have for IS on the 24-70 is somewhat difficult to understand and I wonder if it is based on real world experience or just theoretical thinking. When I first bought it, it replaced my 24-105 f4 IS as my standard walk-around lens, and I thought I would miss both the 70-105 range and IS. The truth is I don´t. I have a very low threshold for buying the latest and greatest, but I don´t see how IS on this lens would tempt me.
About 2/3 of my shots with my 24-105 are taken below the 1/f rule, and I have taken shots as slow as 2-seconds handheld with that lens. I normally consider 1/10th to be my limit at 105mm and 1/2 second at 24mm. Which would you rather have, 1/2 second, ISO 800 or 1/30th ISO 12800 with the same motion blur?