Fedora release 12 became available to the public November 17, 2009. New features are plentiful and many are centred around KVM virtualization.
If you are like me and still running Fedora 10 or 11 and do not wish to wait till a yum based update is pushed out you can kick off your adventure into Fedora 12 land manually. Set aside at least an hour of time where you will not be able to use the PC while the update is taking place. First thing is to review Preupgrade Wiki Page, once you feel confident that your system is ready (enough space in /boot, created backups of your data) issue (as root):
After a lengthy download, reboot and update process you should be looking at Fedora 12 login prompt.
If you used ext3 filesystem in your Fedora 10/11 system you can also migrate to ext4 filesystem by following the Fedora ext4 Wiki guide.