The next version of Windows Mobile that used to be called Windows Mobile 6.5, is now referred to as Windows Phone. They will not refer to the build number going forward. Check out this video demo done by the Inquirer for further explanation.

The new interface is based on the Zune and has quite a few similarities to the iPhone and Palm Pre. As you'd expect, scrolling around the OS is handled by your fingertips rather than hardware buttons.

This is said to be the final build of Windows Phone and it looks pretty slick.