No one really knows what the 24-70 II is like, but based on the MTF charts and the few bits I've heard from people that played with it (most of them just briefly) it's an amazing lens. The 24-70mm 1 is a great lens as well but I've seen quite a bit of variation from copy to copy, some are much sharper than others.
But I agree with most on here, 17-55 for APS-C and 24-70 or 24-105 for FF (depends on your needs and available lenses really).