Microsoft has revised the Vista roadmap, "with business availability in November 2006 and broad consumer availability in January 2007". Unlike many reports, Vista itself isn't slipping - this is just the timetable for consumer release.
And as Colin explains, this might not actually be such a bad thing:
While some may say that a January launch at the retail level means that we are missing the Christmas market a holiday launch for something like doesn't make sense. The number of new machine purchases causes enough of a support headache over the holiday period as it is - adding on a major product launch will overload the system. It makes sense to wait until the new year, after the Christmas rush.
Good to see some people actually read the press release!