It's damned hard to argue against the 24-105 kit with the 5DIII.
Pick any single type or aspect of photography and it's trivial to find a superior lens. But there's still not a single lens that can do everything the 24-105 does, and the 24-105 does it all really well.
Sure, it's not as fast as the 24-70 f/2.8. But it's longer and stabilized. Sure, any single prime is better at that focal length. But you've got a whole bag full o' primes with the 24-105. Sure, f/4 isn't blazing fast. But between its IS and the 5DIII's high ISO ability it's got the low light area covered really well, and most of the time you want to stop down for sharpness and depth of field anyway. Sure, the 24-105 doesn't have the best image quality in the lineup...but it's really close, not that far off at all.
Give me a choice between a 24-105 and a bag o' primes and a sherpa to carry them and an assistant to swap them, and I'll ditch the 24-105. And if I have something specific in mind, I'll grab the special-porpoise tool best suited for that task.
But, if I don't know what I might get into, if I'm looking for a walkabout lens, I'm either reaching for the 24-105 to be prepared for most anything, or I'm taking off the grip and BlackRapid strap and replacing it with a wrist strap and the Shorty McForty to turn the camera into a rich man's slightly-oversized P&S.