Batelle pointed to a review about Windows Vista. Reading these previews makes me more and more sure that my next computer will be a Mac. Vista is the most bureaucratically bloated OS of all time. The 'Ultimate' edition beta is over 10GB in size. It's written by bureaucrats for bureaucrats.
Here are some random datapoints on why Vista will suck:
What Vista won't do is make your computer feel fast. And since my 1yr-old 2.8GHz Win XP Dell with 1GB of RAM already feels like mousing through molasses, upgrading to slower is not for me...
So I think the Vista upgrade cycle is gonna be a great thing for Apple.