David Matthews has released Poly/ML 5.6 on 25-Jan-2016. Poly/ML is one of the oldest and most sophisticated implementations of Standard ML. It routinely supports multi-threading with true parallelism on multicore hardware, fast incremental compilation, source-level debugging. The latest release is also notable for native support on Windows (32/64 bit).
Poly/ML 5.6 is used for Isabelle2016 (February 2016).