Due to moving of the /lib symlink from the glibc package to the more appropriate filesystem package, it is required to update glibc-2.17-2 and filesystem-2013.01-1 together. This will happen automatically when you run "pacman -Syu". Remember, partial updates are not supported and never use the "--force" option...
A potential issue with the upgrade on x86_64 is finding conflicting files in /usr/lib64. All Arch Linux packages that had files in this directory have been updated, so update these individually first. Any AUR packages with files in this directory should be updated to install them in /usr/lib.