There was a regression in udev-168 where "udevadm settle" would
sometimes return too early. This lead to some (apparently rare)
systems being unable to boot, especially people booting from usb
drives or not having devtmpfs support in their kernels were affected.
udev-168-2 contains the fix packported from upstream git.
Please test and signoff both arches, I hope to push to [core]