The Maximus V Extreme is meant for people that enjoy extreme overclocking, preferably with liquid nitrogen or dry ice. The motherboard has an LN2 Mode that you can enable by flipping a switch. What it does exactly weren't quite able to establish, but ASUS says it optimises the board in order to run more stable at extremely low temperatures.
The most innovative feature on the Maximus V Extreme we already saw on the Rampage IV Extreme X79 motherboard: de OC Key. It's a small module that you can connect to the DVI output on your graphics card to which you then connect the monitor. OC Key then shows you all overclocking data (clock frequencies, voltages and temperatures) as an on-screen display on top of the normal image. With a special button on the back of the motherboard you can use your keyboard to navigate through the OC Key menus. This lets you adjust all overclock settings in real-time directly in the hardware, entirely outside of the OS. You can do this while you are running benchmarks. It will keep working even when Windows gives you the BSOD.
Overclockers that employ sub-zero cooling such as dry ice and liquid nitrogen have use of another feature that we saw already on the Rampage IV Extreme motherboard. Next to the SATA ports there is a connector to which you can connector two temperature sensors, of the same type that are used by companies such as Fluke. You can read off the values in the BIOS, with the software and via OC Key. It saves you from having to buy two (often) expensive separate temperature meters, but you do of course have to get the sensors yourself. We checked, and the deviation between what the Maximus V Extreme and an expensive Fluke meter measure at LN2 temperatures is no more than 1 degree. Accurate enough, in other words.
VGA Hotwire was the third new overclocking feature ASUS introduced with the Rampage IV Extreme, and it's present on the Maximus V Extreme as well. If you want to volt mod graphics cards, you can connect the cable to the motherboard. Through the BIOS and OC Key you can monitor and adjust the voltages of the graphics card. The manual clearly indicates which cables go where.
The EFI-BIOS comes in traditional RoG style and is extremely comprehensive in terms of configuration options. The screenshots below give a good impression of all the available options.