Remove 'rhgb quiet' from the kernel command line in the grub config and add 'debug'. The system will mostly hang right after it says 'Welcome to $DISTRO'. It isn't completely dead, as I still get one log line every minute or so. But 10 minutes the system is clearly not booted and has made no visible progress. I wonder if there is a sleep 60 type line in the debug code path somewhere?
Seem that systemd's own logging gets stuck in the filled-up journal socket, before the journal is started, and tools only log in 1/min frequency. :) This seems to make it work for me: http://cgit.freedesktop.org/systemd/systemd/commit/?id=bd6d2963396061ed068c4c6c54d8104b59ba91dc
systemd-207-1.fc20 has been submitted as an update for Fedora 20. https://admin.fedoraproject.org/updates/systemd-207-1.fc20
systemd-207-1.fc20 has been pushed to the Fedora 20 stable repository. If problems still persist, please make note of it in this bug report.