Some updates after sleeping on it and trying some morning debugging:
- It's actually either service being enabled that prevents login
- It's a gnome-shell issue. Logging into a tty is fine, and shows that it's gnome-shell crashing when trying to log-in normally
Maybe it's time to go back to debian...
Its actually GNU image manipulation program, so pretty much.
Or "Green Is My Pepper" if you ask RMS...