Since Beta 2 the following changes have been made, from the bottom of the stack to the top:
grub2 was updated to 2.0 final, notably fixing serial console support by respecting the console width. Its branding was also updated. There were fixes to udev, and to udisks and udisks2 to hide LVM RAID partitions, and many fixes came to autofs from an updated upstream patch.
A lot of systemd fixes came in, including a crash and memleak fix when rotating journals. Many packages now include systemd unit files natively, so these were removed from the systemd package itself, for example for Plymouth, which has been updated to 0.8.5.1. rpm now calls systemctl daemon-reload when installing new init scripts.