1) Anyone buying Windows 7 right now gets an upgrade to Windows 8 (i think either free or 15 dollars)
2) Anyone with Windows XP or higher can get the upgrade version for 40 bucks
3) It will be released on 3 form factors of tablet, laptop, and desktop
4) Metro aside, there have been many improvements to the desktop experience and underlying archetecture of Windows (task manager, file copy, drive storage pools, acct sync across devices, etc..)
5) It boots faster, runs faster, and uses less memory than Win7
6) Any hardware that was compatible with Vista should work fine, and most stuff from the XP era will also work assuming 64 bit drivers were made at some point for Vista/Win7
7) For the first time ever, Microsoft is making their own hardware PC device that will come without a bunch of bloatware like your standard Dell and HP system
8) The only real alternative is to get a Mac, and for compatibility or price reasons, that might not be a valid option.