Yes indeed - it might just be the emperor's new clothes, but I feel that the images from the 24-70 have more 'zing' about them. Certainly, my copy of the kit lens has sharper corners (but I think I was lucky with the kit lens!).
I'll try and do some comparisons, but time is rather tight at the moment. . . . . . Perhaps Tim should do it (after all, he's much better at this stuff than I am) Tim . . . Tim . . . . . Tiiim
all the best