Encountered a new issue on login today. When I left the computer yesterday I locked it with Super + L. (The new lock screen looks great, btw). And this morning when I tried to log in, I was unable to do so. I kept getting "Login failed", even though the password appeared correct. I had to reboot in order to log in. After rebooting, subsequent tests (lock, try to log in) also gave the "login failed" error text next to the "Unlock" button.
Testing with a fresh user now, will report back momentarily.
EDIT: Same behavior with a brand new user. I can lock the screen, but can't unlock except through slick-greeter.