Since I am using i3 window manager for a while and I am very happy with it, I have switched from GDM over to LightDM. Installation was easy:

# sudo yum -y install lightdm-gtk
# sudo systemctl disable gdm.service
# sudo systemctl enable lightdm.service
# sudo reboot


This should work for Fedora 17+ I guess. Tested on 18 tho.