Though not an official release, Build 8014 ISOs are frequently found in archival repositories.
Collectors and historians study this build because it showcases the "in-between" stage of Windows. It lacks the polish of the final 2012 release but includes experimental features that never made it to the final version, such as specific placeholder icons and the unique behavior of the early Charms bar.
It is Windows 8 in its larval stage: ugly, uncertain, but full of potential.