Also, before anyone points to previous messages saying that udev will continue to be usable without systemd, they're out of date. Lennart Poettering currently intends to make systemd a requirement to use udev and expects applications to use the new systemd-only way of calling into udev directly, so that distros can't even fork udev or use an older version to get around the issue. See http://www.phoronix.com/scan.php?page=news_item&px=MTczNjI