For every business you can name I think we could come up with 100 that won't be upgrading straight away. This is always the case with new OSes. Who wants to be on the bleeding edge? In this respect, Vista is no better or worse than any other OS.
Four years after the release of Windows XP, a study showed that half of all businesses were still running Windows 2000.
I'm sorry to put it like this, but this particular statement is nonsense.
Vista hasn't RTM'd yet, and last week Steve Ballmer said the "January" ship date could slip further.
So there is no way you can know whether Dell will ship laptops with Vista at Christmas, since MSFT doesn't know whether they'll have released Vista by then. Over and over again, MSFT has said that Vista will ship when it's ready (an approach I agree with 100%). Trust me, in this particular beta program there is a lot going on behind the scenes, and it isn't all sweetness and light.