The bug is still an issue on herd5, but running the update-initramfs -u -k all on initial boot (after using the 'break=mount' trick) system now boots properly. There was no /var/lib/mdadm/CONF-UNCHECKED though.
Hopefully this can be automated for release :) -- mdadm broken after feisty upgrade, no boot https://launchpad.net/bugs/83050 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
