Comment 14 for bug 1569357

I am not entirely sure what corrected the problem, but here are all of the steps I performed:

sudo apt-get install lightdm
sudo dpkg-reconfigure lightdm
sudo systemctl enable lightdm.service
sudo reboot

rm -rf .cache/compizconfig-1
rm -rf .compiz
rm -rf .Xauthority
rm -rf .config/autostart
dconf reset -f /org/compiz
setsid unity

At this point, Unity sprang to life for me.