Worth noting - the 24-70/4 IS is almost a true macro lens.I use my 24-105mmL for product photography, and its mfd is not as close as I'd like. Since the camera is bolted to a heavy table, the IS doesn't come into play, but mfd does.
If those specs are true, a 0.7x max mag of the 24-70/4 is pretty darn close to a true 1:1 macro, and much higher than any other non-macro lens in the lineup (the 24-105 is 0.3x, 24-70 is 0.29x, 24-70 II is 0.21x). It's even higher than the 50mm f/2.5 Compact Macro. The use of H-IS would be consistent with that high max mag (the only other lens that has it is the 100L Macro, but PowerShots also have H-IS since they have very close MFDs).
So, this lens is a combination general purpose zoom and near-macro lens, something nonexistent in the current lineup. For people who like to shoot close ups (flowers, jewelry, etc.) this is like getting two lenses in one.
I have the 100L, and I like the longer working distance, so its not likkely to go away.
I can see a 2 lens travel combination of 24-70 f/4 and 70-300L being pretty handy.