2014 was an extremely busy fullframe year for Nikon, releasing three new cameras, including the D810, the D610 (they kind-of had to ) and the D750. Much like their APS-C sized DX range, Nikon's FX full frame range is now starting to offer a bit of everything – if you have the dosh to cross over.
As expected awesome photo quality; High ISO remains usable; Tilt-out screen makes it awesome for videographers
Actually not a lot although price comes to mind