I don't know why the C6 demo isn't out yet. But as others have said(and not just on this forum), C6 is much better than C5, even if just for the Dynamic Hair/NLA in C6.
I have worked with A:M 9.0 and Shade 8.5 etc, and for the GUI and ease of use, C6 puts them to shame(imho). A:M does have some nice animation/modeling workflows though, but I just couldn't get into it like Carrara. Its all about how the app/tool fits the person I guess. ;)