As said in the ArchLinux.org announcement, this updated install media has dropped AIF, the Arch Installation Framework. AIF has been replaced by some simple install scripts rather than a menu-driven installer. The Arch Installation Framework was dropped due to lack of maintenance and contributions by developers.
Rather than dropping six different install images like in the past, Arch Linux is moving to a single image that can be booted on i686 or x86_64 hadware. Media containing Arch's "core" repository is also no longer available.
Going forward, Arch Linux plans to provide new install media on a monthly basis.
Download Arch Linux here.