I'm very surprised to read all the negativity about the 24-70mm (although it's really only coming from a couple of you), considering its reputation as a great lens. I don't know how good my copy of this lens is, but it seems fine to me - I bought mine from Adorama in 2007. The AF speed on it is blistering and it's built like a tank!There definitely are good copies out there, hopefully and very likely more good than bad. There has never been any question over the build quality and the AF speed...it's the dodgy optics that have traumatized far too many photographers. The negative experience is not just coming from a couple of people on this thread, it's been in the spotlight on this and various other forums/lists/professional associations etc for years.
The 24-70 f/2.8 really was the hot candidate for a major refresh, and the MkII sounds like a cracker.