Was worth a try... I got the black screen of death.
Had to ctrl-alt-del to restart cleanly.
For anyone else with Fedora who falls into same predicament: after rebooting hit "a" button at grub prompt and append "single" (no quotes) to the line that appears and then hit enter. Once you're at the # prompt type:
chkconfig nvidia off
You might also have to edit /etc/X11/xorg.conf to use VESA driver if you compiled yourself, but with Livna's binary I didn't have to. Just did a "yum remove kmod-nvidia" and the mess was cleaned up for me.