i am very happy with the 24-105 as an all-round lens with the 5D
it does vignet pretty badly at f4 24mm and noticeable at 5.6
a bit soft from 24-40, but very sharp at the long end
if you're photographing action in low light, then the 24-70 f2.8 will be better, but then heavier and not as useful all-round
i was very suprised to find that my old 24-85 is nearly as sharp as the 25-105 (with the same vignetting) - a nice, light walking around lens in good light