For my system I needed to apply the intel microcode in order for Gnome to work. If I didn’t, when I tried to login I would get “Oh no! Something has gone wrong”.
To apply the microcode for all I needed to do was:
# pacman -S intel-ucode
# grub-mkconfig -o /boot/grub/grub.cfg
# reboot
https://wiki.archlinux.org/index.php/Microcode#Grub
Maybe this post will help others who run into this problem.
