"This 7.2.2 release is intended to be more of a "technology preview" than normal GHC stable branches. In particular, it supports a significantly improved version of DPH, as well as new features such as compiler plugins and "safe Haskell". The design of these new features may evolve as we get more experience with them. "
http://www.haskell.org/ghc/download_ghc_7_2_2
