I just finished reinstalling f16alpha from a usb device to a Acer Aspire One. Ran yum update --skip-broken and all 400+ packages updated.
The grub2 was 1:1.99-5.fc16 rebooted to a login screen, entered psswd and got "OH NO! blah blah blah" re-logged in and was able to get the desktop then.
I did not run "grub2-update" or "grub2-install /dev/sda" before rebooting. On the second reboot all went well at the login screen with no error/warning. Shutting down and calling it a night.