Two days ago, Intel added a new BIOS for the NUC to their download center. Its main update addresses a problem with booting some operating systems, such as SteamOS. Ars Technica published an editorial a couple of weeks ago about using the Haswell-based NUC with four Linux distributions. It basically comes down to the NUC not seeing a bootloader file that Debian-based OSes leave in their own branded folder. The BIOS was available less than two weeks later.
The update also addresses (PDF) fan speed control, a bug with disk encryption passwords, a couple of BIOS settings, and a system hang with certain USB thumb drives.
If you have a NUC and want to make it a SteamOS (or Ubuntu, etc.) device, this should fix your woes. I mean, there was already a workaround involving four terminal commands but it is that much easier nonetheless. It is available now at Intel's store.