Parts of it are implemented. But parts of it aren't, and there have been similar cases where something was standardized but never got implemented (e.g. CSS2.1). I'm coming more and more to the position that standardization should happen after implementation rather than before.
Will be implemented and the important bits are already implemented everywhere except GCC, claims of GCC compliance aside. Like, take the standard library for a second--only on GCC must I care about std::unordered_map versus std::tr1::unordered_map. That's a minor pain, but I don't care--I don't feel like dealing with it for GCC platforms (especially given that even after libstdc++ gets right there will be old versions floating around), so I'm only targeting Windows and OS X where clang and libc++ is available.
