According to ASUS the Rampage III Extreme is "Designed for those who know the Dark Art of Overclocking". It comes equipped with all features that overclockers dream of, and also has new stuff like ROG Connect for example.
The board supports CPUs for Intel Socket 1366, which means Core i7 including Gulftown (yes, I asked). As chipset Intel's X58 and ICH10R is used like on the Rampage II Extreme. ASUS has routed 32 PCI-Express 2.0 lanes to the PCI-E x16 slots, so you can either run x16+x16, x16+x8+x8 or x8+x8+x8+x8 - all without the added heat and latency of NVIDIA's nForce 200. As we hear this does make quite a difference in a 4x HD 5870 configuration for example. Major improvements have also been made to the power solution which is now 8-phase digital 250 - 1000 kHz. Of course support for USB 3.0 and SATA 6 Gb/s is included as well.While exact details are not known, the price of the board will be "highest priced ROG" - my guess is around $400, with availability starting around the Gulftown launch which should be some time in March.

Big, big picture, about 5 MB, can be found here.