You might have noticed that the Platform Preview release for IE10 was only compatible with Windows 7. Well, if you're a Vista user, you're not only out of luck with the Platform Preview, but also with the final release.
Here's the official word, straight from a Microsoft spokesperson:
Windows Vista customers have a great browsing experience with IE9, but in building IE10 we are focused on continuing to drive the kind of innovation that only happens when you take advantage of the ongoing improvements in modern operating systems and modern hardware.
So, not only will IE10 leave XP users out in the cold, but also Vista users.