Since not all of us are lucky enough to get to directly ask Microsoft engineers questions about Windows Vista, Gina from Lifehacker will have to be our surrogate. And what a fine surrogate she is.
She pelted Microsoft with questions like "why should I upgrade to Vista", "how long will XP be supported", "why did you make so many Vista versions", and "is Vista an innovation, or is it playing catch-up with OS X?" Not all the questions got a straight answer, but there are some good nuggets here that will help you decide whether you want to upgrade to Vista sooner rather than later.
Q&A with Microsoft about Windows Vista [Lifehacker]